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Articles by Ian Q. Whishaw in JoVE

 JoVE General

Rat fimbria-forniks Lezyonlar Koku Takibi sonra ancak Engelli Dead Reckoning Pilotaj Korunan bir video gösteri


JoVE 1193 4/24/2009

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Department of Neuroscience, Canadian Centre for Behavioural Neuroscience, University of Lethbridge

Bir pilot koku izleme görevi sıçan, gıda ile görsel bir koku izi kullanarak ya da kızılötesi ışık kullanarak ölü hesaplaşma bir sığınak dönmek için yetenek, önceki hareketleri entegre kayıt, hipokampus ölü hesaplaşma için gerekli olduğunu göstermektedir.

Other articles by Ian Q. Whishaw on PubMed

Is There an Optimal Age for Recovery from Motor Cortex Lesions? II. Behavioural and Anatomical Consequences of Unilateral Motor Cortex Lesions in Perinatal, Infant, and Adult Rats

Restorative Neurology and Neuroscience. 2000  |  Pubmed ID: 11490078

Purpose: The purpose of this study was to compare the behavioural and anatomical effects of unilateral motor cortex ablation in neonatal, infant, and adult rats. Methods: Rats were given unilateral lesions of the motor cortex on the day of birth (P1), at ten days of age (P10), or in adulthood. They were trained on several motor tasks (skilled forelimb reaching, beam traversing, tongue extension), general motor activity, and a test of spatial learning (Morris water task). Results: Although all lesion groups were equally impaired at skilled reaching with the forelimb contralateral to the lesion, rats with P1 lesions also were impaired at traversing a narrow beam and at learning the Morris task. Gross anatomical analyses revealed that the P1 rats had smaller brains than the other groups, a result that may account for the larger behavioural deficits in the P1 group. Analysis of Golgi-Cox stained neurons showed that relative to control groups, all lesion groups showed an increase in dendritic length in the basilar dendrites of layer III pyramidal cells and, paradoxically a decrease in length of the apical dendrites of the same cells. Conclusions: The bilateral alterations in dendritic organization following the motor cortex lesions suggest that there has been a bilateral reor-ganization of intrinsic cortical connectivity following motor cortex lesions at any age. These alterations in connectivity are likely not identical in the young and adult animals, however, because relative to controls, both the young operated groups, but not the adult group, showed a bilat-eral drop in spine density in the basilar dendrites of layer V pyramidal cells. These findings are discussed with respect to the idea that there may be critical ages in development in which animals can use anatomical modifications to compensate for deficits produced by cortical injury.

Quantification of a Single Exploratory Trip Reveals Hippocampal Formation Mediated Dead Reckoning

Journal of Neuroscience Methods. Jan, 2002  |  Pubmed ID: 11772435

A rat's proclivity to explore a novel environment presents a behaviorally rich paradigm to investigate the role of the hippocampus in spatial navigation. Here we describe a novel technique of behavioral analysis that is derived from a single exploratory trip. An exploratory trip was defined as a rat's departure from the home base that ended when the rat returned to the home base. The behavior observed on a single exploratory trip by a control animal is highly organized into outward and homeward segments. An outward segment is characterized by a slow circuitous progression from the home base marked by several stops. A homeward segment is characterized by a rapid direct return to the home base. The velocity attribute of the exploratory trip was quantified by estimating the point of inflection associated with the trip's cumulative moment-to-moment velocity distribution. The heading direction and variance of the homeward trip segment was analyzed with circular statistics. A comparison of the exploratory behavior of control animals and animals with damage to the fimbria-fornix indicated that the velocity and heading direction of the homeward portion of the trip depends upon the hippocampal formation. While control and fimbria-fornix rats had similar outward segments, the return paths of the fimbria-fornix rats were significantly slower, more circuitous, and more variable compared with that of the control rats. This result was also independent of testing in light or dark conditions. The lack of dependence on allothetic cues suggests that rats employ dead reckoning navigational strategies to initiate the homeward portion of exploratory movements. Methods to quantify exploratory behavior in terms of velocity and angular components provide an assessment of control behavior and the assessment of the behavior of rats with hippocampal formation damage that is easy to implement.

DREAM is a Critical Transcriptional Repressor for Pain Modulation

Cell. Jan, 2002  |  Pubmed ID: 11792319

Control and treatment of chronic pain remain major clinical challenges. Progress may be facilitated by a greater understanding of the mechanisms underlying pain processing. Here we show that the calcium-sensing protein DREAM is a transcriptional repressor involved in modulating pain. dream(-/-) mice displayed markedly reduced responses in models of acute thermal, mechanical, and visceral pain. dream(-/-) mice also exhibited reduced pain behaviors in models of chronic neuropathic and inflammatory pain. However, dream(-/-) mice showed no major defects in motor function or learning and memory. Mice lacking DREAM had elevated levels of prodynorphin mRNA and dynorphin A peptides in the spinal cord, and the reduction of pain behaviors in dream(-/-) mice was mediated through dynorphin-selective kappa (kappa)-opiate receptors. Thus, DREAM appears to be a critical transcriptional repressor in pain processing.

Impaired Spatial Performance in Rats with Retrosplenial Lesions: Importance of the Spatial Problem and the Rat Strain in Identifying Lesion Effects in a Swimming Pool

The Journal of Neuroscience : the Official Journal of the Society for Neuroscience. Feb, 2002  |  Pubmed ID: 11826144

Behavioral, electrophysiological, and anatomical evidence suggests that retrosplenial (RS) cortex (areas RSA and RSG) plays a role in spatial navigation. This conclusion has been questioned in recent work, suggesting that it is damage to the underlying cingulum bundle (CG) (areas CG and IG), and not RS, that disrupts spatial place learning (Aggleton et al., 2000). We revisited this issue by comparing Long-Evans rats, the strain used in studies that report RS deficits, to Dark Agouti rats, the strain in which no RS deficit has been reported. Rat groups with RS, RS + CG, or no lesion were tested on a place task in a swimming pool, a test of nonspatial and spatial learning, and a matching-to-place task, a relatively selective test of spatial learning. Long-Evans rats given RS and RS + CG lesions, either before or after training on the two tasks, were impaired on both tasks, a deficit not attributable to impaired visual acuity. Control Dark Agouti rats and RS Dark Agouti rats, although not different on the place task, were both significantly impaired relative to Long-Evans rats. The RS Dark Agouti group, however, was also impaired on the matching-to-place task. Thus, we show that RS cortex is part of an extended neural circuit involved in spatial behavior in both Long-Evans and Dark Agouti rats, but its role in the place task may be masked by an innate nonspatial deficit in Dark Agouti rats. The results are discussed in relation to the importance of assessing spatial learning with appropriate spatial tests, the problems of interpretation posed by rat strain differences, and the role of retrosplenial cortex in spatial behavior.

Rats Can Track Odors, Other Rats, and Themselves: Implications for the Study of Spatial Behavior

Behavioural Brain Research. Apr, 2002  |  Pubmed ID: 11844585

In order to demonstrate that rats solve dead reckoning (path integration) tasks in which they return to a starting location using self-movement (idiothetic) cues, it is necessary to remove external (allothetic) cues. Odor cues, especially those generated by a rat on a single passage, are difficult to control and they can potentially serve as a cue to guide a homeward trip. Because it is presently unknown whether rats can track the cues that they themselves leave, as opposed to the odor trails left by other rats, we investigated this question in the present study. A tracking task was used in which rats: (1) followed a scented string from a refuge to obtain a food pellet located on a large circular table; (2) followed odors left on the table; (3) followed odors left by the passage of another rat; or (4) followed odors left by themselves. Groups of rats were presented with strings scented with either the rat's own odor (Group Own), a conspecific's odor (Group Other), or another scent, vanilla (Group Vanilla). After training, a series of discrimination tests were given to determine the nature of the stimulus that controls scent tracking. The results indicated that Own, Other, and Vanilla groups were equally proficient in discriminating and following their respective odors. The rats were also able to follow odor trails on the table surface as well as a trail left by the single passage of another rat or their own passage. This is the first study to demonstrate that rats can discriminate between conspecific odors and their own odor left during a single passage. The results are discussed in relation to their implications for experimental methodology and olfactory contributions to spatial navigation in general and dead reckoning in particular.

Impaired Dodging in Food-conflict Following Fimbria-fornix Transection in Rats: a Novel Hippocampal Formation Deficit

Brain Research Bulletin. Mar, 2002  |  Pubmed ID: 11927357

It is well known that damage to the hippocampal formation (Ammon's horn, dentate gyrus, fimbria-fornix, and other pathways) produces impairments in spatial navigation and in certain forms of learning. Lesions within these structures have also been reported to produce some motor impairments, but the nature of these impairments is less understood. The present study examined the effects of fimbria-fornix lesions on food wrenching and dodging, social interactions that occur when one rat attempts to steal food from a conspecific, who in turn attempts to protect the food by an evasive movement. Lesion effectiveness was confirmed histologically and electrophysiologically, by the loss of hippocampal rhythmical slow-wave activity (RSA or theta), and by changes in open field behavior (increased open field behavior, less thigmotaxis and more defecation). Analysis of the social interaction indicated when an eating control rat was approached by a conspecific that was attempting to steal its food, it prevented the theft by dodging, a rapid lateral maneuver involving forequarter turning and stepping with the rear limbs. Rats with fimbria-fornix lesions were significantly impaired in dodging and so were more likely to lose their food to the robber. This novel deficit in motor behavior is discussed in relation to contemporary theories of hippocampal function and it is suggested that the deficit may be caused by an inability of the fimbria-fornix damaged animals to disengage attention from eating in order to initiate an evasive movement to protect food. The finding of this novel deficit underscores the importance of considering both loss as well as release phenomena in the analysis of hippocampal formation function.

Cortical and Subcortical Lesions Impair Skilled Walking in the Ladder Rung Walking Test: a New Task to Evaluate Fore- and Hindlimb Stepping, Placing, and Co-ordination

Journal of Neuroscience Methods. Apr, 2002  |  Pubmed ID: 11992668

The ladder rung walking test is a new task to assess skilled walking and measure both forelimb and hindlimb placing, stepping, and inter-limb co-ordination. Rats spontaneously walk from a starting location to a goal along a horizontal ladder. The spacing between the rungs of the ladder is variable and can be changed to prevent the animal from learning either the absolute or relative location of the rungs. The testing procedure requires minimal training and allows detailed quantitative and qualitative analysis using video recording. The utility of the test is described with postoperative data obtained from animals with unilateral neocortical strokes produced by pial stripping over the motor cortex, neonatal and adult unilateral corticospinal tract lesions produced by tract section at the pyramids, and unilateral dopamine depletions produced by injection of 6-hydroxydopamine into the nigrostriatal bundle. In addition, a group of aged rats was examined. Deficits in limb placing, stepping and co-ordination displayed by the animals demonstrate that this test can discriminate between lesions of the motor system or age-associated impairments. The test is useful for assessing loss and recovery of function due to brain or spinal cord injury, the effectiveness of treatment therapies, as well as compensatory processes through which animals adapt to nervous system injury.

Animal Models of Neurological Deficits: How Relevant is the Rat?

Nature Reviews. Neuroscience. Jul, 2002  |  Pubmed ID: 12094213

Animal models of neurological deficits are essential for the assessment of new therapeutic options. It has been suggested that rats are not as appropriate as primates for the symptomatic modelling of disease, but a large body of data argues against this view. Comparative analyses of movements in rats and primates show homology of many motor patterns across species. Advances have been made in identifying rat equivalents of akinesia, tremor, postural deficits and dyskinesia, which are relevant to Parkinson's disease. Rat models of hemiplegia, neglect and tactile extinction are useful in assessing the outcome of ischaemic or traumatic brain injury, and in monitoring the effects of therapeutic interventions. Studies in rodents that emphasize careful behavioural analysis should continue to be developed as effective and inexpensive models that complement studies in primates.

Quantitative and Qualitative Impairments in Skilled Reaching in the Mouse (Mus Musculus) After a Focal Motor Cortex Stroke

Stroke; a Journal of Cerebral Circulation. Jul, 2002  |  Pubmed ID: 12105368

Skilled reaching movements are an important aspect of human motor behavior but are impaired after motor system stroke. The purpose of this study was to document skilled movements in mice before and after a focal motor cortex stroke for the purpose of developing a mouse model of human stroke.

Impairment of Pronation, Supination, and Body Co-ordination in Reach-to-grasp Tasks in Human Parkinson's Disease (PD) Reveals Homology to Deficits in Animal Models

Behavioural Brain Research. Jul, 2002  |  Pubmed ID: 12110450

Animal (monkey, rat, mouse) models are widely used to investigate degenerative processes and potential therapeutic treatments for human Parkinson's disease (PD). One task that has proved useful in these investigations is a reach-to-grasp task (skilled reaching) in which an animal reaches for a piece of food that it then consumes. Rats with extensive unilateral Dopamine depletions are impaired in using the contralateral limb. The qualitative features of posture, lifting and advancing the limb, pronating the paw to grasp food, and in withdrawing and supinating the paw to place the food in the mouth are impaired, as is reaching success. Humans with PD are often described as having poor manual dexterity that worsens as the disease progresses. As there have been no detailed comparisons of reaching movements in the animal models and in PD subjects, the following descriptive analysis was performed. Ten subjects with PD, eight age matched controls and 14 young normal subjects were studied as they used a natural movement of reaching for a small piece of food that they then placed in the mouth to eat. The reaching movements were described using Eshkol-Wachman Movement Notation (EWMN), supplemented with kinematic analyses. From this description, a 21-point rating scale was devised to describe the component movements of the reach. Movements included: orienting the head and eyes to the target, adjusting posture, lifting the hand, shaping and aiming the digits to the target, pronating the hand to grasping the food with a pincer grip, lifting and supinating the hand to transporting the food to the mouth, and further supinating the hand and opening the digits to place food in the mouth, and finally returning the hand to the starting position. Analysis indicated that most aspects of the reaching movements of the PD subjects were significantly different relative to both young control subjects and old control subjects. As compared to the control groups, postural and reaching components of the movements were fragmented, movements were achieved using more proximal segments of the body, and rotatory movements of the hand were limited. The PD subjects did use a pincer grasp to obtain the food, but the grasp was less independent of other digit movements than was observed in the control subjects. These results are discussed in terms of a homology to impairments displayed animal models of PD.

Absence of Impairments or Recovery Mediated by the Uncrossed Pyramidal Tract in the Rat Versus Enduring Deficits Produced by the Crossed Pyramidal Tract

Behavioural Brain Research. Aug, 2002  |  Pubmed ID: 12191820

The pyramidal tract of the rat consists of at least two components. A majority of the fibers cross in the lower medulla and descend through the spinal cord in the ventral portion of the dorsal funiculus. The remaining 5% of the corticospinal projection does not cross and descends in the ipsilateral ventral funiculus into the cervical spinal region where its projections terminate in the internuncial portions of the spinal gray matter. The anatomical origin and terminal distribution of the ipsilateral component suggests that it may be involved in the control of the ipsilateral limb, but the possible contribution of the ipsilateral corticospinal tract has not been systematically examined. To determine whether the ipsilateral corticospinal tract makes a contribution to skilled movement, the corticospinal tract was severed unilaterally at the medullary level rostral to the decussation, thus severing both the crossed component of the tract as well as the ipsilateral component. Performance of the ipsilateral and the contralateral limbs of rats were then evaluated on tests of limb posture, preference, placing, and use in two skilled reaching tasks. No impairments on any quantitative or qualitative measure of performance were detected in the use of the limb ipsilateral to the lesion but severe, enduring impairments on all qualitative and quantitative measures were obtained in use of the limb contralateral to the lesion. Thus, the study finds: (1) no evidence that the ipsilateral portion of the corticospinal tract makes a contribution to skilled movement of the kind made by the contralateral portion of the corticospinal tract, and (2) no evidence that the remaining uncrossed portion of the tract contributes to recovery of symptoms produced by severing the crossed portion of the tract.

Place and Matching-to-place Spatial Learning Affected by Rat Inbreeding (Dark-Agouti, Fischer 344) and Albinism (Wistar, Sprague-Dawley) but Not Domestication (wild Rat Vs. Long-Evans, Fischer-Norway)

Behavioural Brain Research. Aug, 2002  |  Pubmed ID: 12191833

Domestication has been shown to produce a shift in both morphological and behavioral characteristics of animals. While changes in body weight, brain size, reproductive rates, and temperament are well documented, the effects of domestication on learning and memory are not as clearly understood. This issue is of particular importance to the use of rodent models in learning and memory where the domestication of Rattus norvegicus for research has resulted in the availability of numerous strains. To investigate cognitive effects resulting frm domestication, we examined the spatial performance of a number of rat strains: wild, Long-Evans, Fischer-Norway, Dark-Agouti, Wistar, Fischer 344, Sprague-Dawley. The wild rats served as a baseline for comparing inbred and outbred domestic strains and pigmented and albino domestic strains. Place (a measure of nonspatial and procedural learning), matching-to-place (spatial working memory), and probe (retention) performance were measured in the Morris swimming pool task. The task is an ideal means for comparing different rat strains because place learning has not been selected for in the domestication of Rattus norvegicus and because the task is ethologically relevant. The results indicated that wild rats and Long-Evans rats did not differ on any measure, with Fischer-Norway rats being only slightly inferior. Larger impairments were found in Wistar > Fischer 344 > Dark-Agouti > Sprague-Dawley strains. Impairments were more obvious on place acquisition but also occurred in matching-to-place performance. Platform crosses, but not quadrant preference was found to be correlated with place learning. In general, although nonspatial and spatial deficits were associated with both inbreeding and albinism, impaired spatial performance is not a necessary result of domestication.

Vestibular Information is Required for Dead Reckoning in the Rat

The Journal of Neuroscience : the Official Journal of the Society for Neuroscience. Nov, 2002  |  Pubmed ID: 12427858

Dead reckoning is an on-line form of spatial navigation used by an animal to identify its present location and return directly to a starting location, even after circuitous outward trips. At present, it is not known which of several self-movement cues (efferent copy from movement commands, proprioceptive information, sensory flow, or vestibular information) are used to compute homeward trajectories. To determine whether vestibular information is important for dead reckoning, the impact of chemical labyrinthectomy was evaluated in a test that demanded on-line computation of a homeward trajectory. Rats were habituated to leave a refuge that was visible from all locations on a circular table to forage for large food pellets, which they carried back to the refuge to eat. Two different probe trials were given: (1) the rats foraged from the same spatial location from a hidden refuge in the light and so were able to use visual cues to navigate; (2) the same procedure took place in the dark, constraining the animals to dead reckon. Although control rats carried food directly and rapidly back to the refuge on both probes, the rats with vestibular lesions were able to do so on the hidden refuge but not on the dark probe. The scores of vestibular reflex tests predicted the dead reckoning deficit. The vestibular animals were also impaired in learning a new piloting task. This is the first unambiguous demonstration that vestibular information is used in dead reckoning and also contributes to piloting.

Variation in Visual Acuity Within Pigmented, and Between Pigmented and Albino Rat Strains

Behavioural Brain Research. Nov, 2002  |  Pubmed ID: 12429395

Many researchers assume that laboratory rats have poor vision, and accordingly, that they need not consider differences in the visual function of rats as a consequence of strain or experience. Currently, it is not specifically known whether rat domestication has negatively affected the visual function of laboratory rat strains, what the effects of strain albinism are on rat visual function, or whether there are strain differences in the visual function of laboratory rats that are independent of pigmentation. In order to address these questions, we measured psychophysically the vertical grating acuity of three pigmented (Dark Agouti, Fisher-Norway, Long-Evans) and three albino (Fisher-344, Sprague-Dawley, Wistar) strains of laboratory rats, and compared their acuity with that of wild rats. The grating thresholds of Dark Agouti, Long-Evans and wild strains clustered around 1.0 cycle/degree (c/d) and did not significantly differ from one another. Fisher-Norway rats, however, had a significantly higher threshold of 1.5 c/d. The grating thresholds of Fisher-344, Sprague-Dawley, and Wistar strains, which were clustered around 0.5 c/d, were significantly lower than those of the pigmented strains. These data demonstrate that there is significant strain variability in the visual function of laboratory rats. Domestication of Long-Evans and Dark Agouti strains does not appear to have compromised visual acuity, but in the case of Fisher-Norway rats, selective breeding may have enhanced their acuity. Strain selection associated with albinism, however, appears to have consistently impaired visual acuity. Therefore, a consideration of strain differences in visual function should accompany the selection of a rat model for behavioral tasks that involve vision, or when comparing visuo-behavioral measurements across rat strains.

Long-Evans Rats Have a Larger Cortical Topographic Representation of Movement Than Fischer-344 Rats: a Microstimulation Study of Motor Cortex in Naïve and Skilled Reaching-trained Rats

Brain Research Bulletin. Nov, 2002  |  Pubmed ID: 12431749

Intracortical microstimulation of the frontal cortex evokes movements in the contralateral limbs, paws, and digits of placental mammals including the laboratory rat. The topographic representation of movement in the rat consists of a rostral forelimb area (RFA), a caudal forelimb area (CFA), and a hind limb area (HLA). The size of these representations can vary between individual animals and the proportional representation of the body parts within regions can also change as a function of experience. To date, there have been no investigations of strain differences in the cortical map of rats, and this was the objective of the present investigation. The effect of cortical stimulation was compared in young male Long-Evans rats and Fischer-344 rats. The overall size of the motor cortex representation was greater in Long-Evans rats compared to Fischer-344 rats and the threshold required to elicit a movement was higher in the Fischer-344 rats. An additional set of animals were trained in a skilled reaching task to rule out the possibility that experiential differences in the groups could account for the result and to examine the relationship between the differences in topography of cortical movement representations and motor performance. The Long-Evans rats were quantitatively and qualitatively better in skilled reaching than the Fischer-344 rats. Also, Long-Evans rats exhibited a relatively larger area of the topographic representation and lower thresholds for eliciting movement in the contralateral forelimb. This is the first study to describe pronounced strain-related differences in the microstimulation-topographic map of the motor cortex. The results are discussed in relation to using strain differences as a way of examining the behavioral, the physiological, and the anatomical organization of the motor system.

Fimbria-fornix Lesions Disrupt the Dead Reckoning (homing) Component of Exploratory Behavior in Mice

Learning & Memory (Cold Spring Harbor, N.Y.). Nov-Dec, 2002  |  Pubmed ID: 12464698

Exploration is the primary way in which rodents gather information about their spatial surroundings. Thus, spatial theories propose that damage to the hippocampus, a structure thought to play a fundamental role in spatial behavior, should disrupt exploration. Exploration in rats is organized. The animals create home bases that are central to exploratory excursions and returns, and hippocampal formation damage alters the organization of exploration by disrupting returns. Mice do not appear to readily establish home bases in novel environments, thus, for this species, it is more difficult to establish the contribution of the hippocampus to exploration. The purpose of the present study was threefold: develop a task in which mice center their exploration from a home base, determine whether the exploratory behavior is organized, and evaluate the role of fimbria-fornix lesions on exploration. Mice were given a novel exploratory task in which their nesting material was placed on a large circular table. Video records of control and fimbria-fornix mice were made in both light and dark (infrared light) conditions. Exploration patterns (outward trips, stops, and homeward trips) were reconstructed from the video records. Control mice centered their activity on their bedding, from which they made circuitous outward trips marked by many stops, and periodic direct returns. The bedding-centered behavior and outward trips of the fimbria-fornix mice were similar to those of the control mice, but significantly fewer direct return trips occurred. The direct homeward trips observed under light and dark conditions were consistent with a dead-reckoning strategy, in which an animal computes its present position and homeward trajectory from self-movement cues generated on the outward trip. Because the fimbria-fornix lesions disrupted the homeward component of exploratory trips, we conclude that the fimbria-fornix may contribute to dead reckoning in mice. The results also show that the home-bedding methodology facilitates the establishment of a home base by mice, thus providing a useful methodology for studies with mice.

On the Origins of Autobiographical Memory

Behavioural Brain Research. Jan, 2003  |  Pubmed ID: 12527442

Tolving argues that one form of explicit memory, autobiographical memory is uniquely human and has no nonhuman animal antecedents. We suggest that a form of memory used by humans and nonhuman animals, dead reckoning, shares a common limbic structure, including the cingulate cortex and hippocampus, and involves similar processes in recognition of self-action. Thus, it may be homologous to, and an antecedent of, autobiographical memory in humans.

A Novel Skilled-reaching Impairment in Paw Supination on the "good" Side of the Hemi-Parkinson Rat Improved with Rehabilitation

The Journal of Neuroscience : the Official Journal of the Society for Neuroscience. Jan, 2003  |  Pubmed ID: 12533618

Parkinson's disease is characterized by tremor, rigidity, bradykinesia, and postural abnormalities ascribed to the loss of nigrostriatal dopamine (DA). Symptoms similar to the human condition can be produced in the rat by DA-depleting 6-hydroxydopamine injections made into the nigrostriatal system. After a unilateral lesion, the rat symptoms include sensory and motor impairments and turning biases reflecting motor abnormalities to the contralateral-to-depletion side of the body. In addition, a number of studies on skilled reaching report impairments in the use of the ipsilateral limb. It is suggested that the ipsilateral deficit is secondary to the contralateral motor impairments however. Here we re-examine how rats with unilateral DA depletion use their ipsilateral limb for skilled reaching for food. We provide the first description of an impairment on the ipsilateral-to-depletion side of the body of the rat and the first demonstration of amelioration of the defect using behavioral therapy. Video analysis of rats reaching for single pellets of food with the ipsilateral limb revealed that, although limb advancement and food grasping were normal, paw supination and food release to the mouth were impaired. Consequently, the animals were unable to transport a grasped food pellet to the mouth. Behavioral therapy, consisting of training in a simpler reaching task, strikingly lessened the impairment and improved reaching movements to the point that the rats could transport the food to the mouth. The results are discussed in relation to possible causes of the ipsilateral impairment, its treatment, and to relevant research on human Parkinson patients, indicating that they display bilateral improvements after unilateral treatments.

Cholinergic and Serotonergic Neocortical Projection Lesions Given Singly or in Combination Cause Only Mild Impairments on Tests of Skilled Movement in Rats: Evaluation of a Model of Dementia

Brain Research. Apr, 2003  |  Pubmed ID: 12706251

The cholinergic (ACh) projections of the nucleus basalis and the serotonergic (5-HT) projections of the raphe nuclei to the neocortex are required for the normal function of the neocortex. Nevertheless, damage to either system alone has little effect on the behavior of rats, but conjoint damage to both systems is reported to produce dementia to the point that animals are described as being unable to engage in intelligent behavior. Because rats with bilateral damage to both systems are so severely impaired, they are not useful for chronic studies. The objective of the present research was to determine whether unilateral depletions produce a functional impairment. Rats received unilateral neurotoxic lesions to either the nucleus basalis (quisqualic acid), or the medial forebrain bundle (5,7-dihydroxytryptamine), or both, which reduced neocortical levels of ACh (55%) and 5-HT (63%). The rats then received a battery of tests sensitive to unilateral neocortical injury. The 5-HT lesion produced no quantitative or qualitative deficits on reaching for food, walking across a horizontal ladder, forelimb placement in a cylinder, sensory detection of adhesive paper applied to the wrists, or forelimb inhibition during swimming. The ACh lesion produced mild qualitative deficits in reaching. Combined lesions produced mild deficits in skilled reaching, ladder walking, and sensory detection. In contrast to the mild impairments produced by the lesions, pharmacological blockade of either ACh with atropine or 5-HT with methiothepin mesylate systemically blocked skilled motor behavior as assessed by skilled reaching. The results are discussed in relation to the problems associated with the development of a unilateral model of dementia.

Distinct Forelimb and Hind Limb Stepping Impairments in Unilateral Dopamine-depleted Rats: Use of the Rotorod As a Method for the Qualitative Analysis of Skilled Walking

Journal of Neuroscience Methods. Jun, 2003  |  Pubmed ID: 12788498

The rotorod test, in which animals walk on a rotating drum, is widely used to assess motor status in laboratory rodents. Performance is measured by the duration that an animal stays up on the drum as a function of drum speed. Here we report that the task provides a rich source of information about qualitative aspects of walking movements. Because movements are performed in a fixed location, they can readily be examined using high-speed video recording methods. The present study was undertaken to examine the potential of the rotorod to reveal qualitative changes in the walking movements of hemi-Parkinson analogue rats, produced by injection of 6-hydroxydopamine (6-OHDA) into the nigrostriatal bundle to deplete nigrostriatal dopamine (DA). Beginning on the day following surgery and then periodically over the next two months, the rats were filmed from frontal, lateral, and posterior views as they walked on the rotorod. Behavior was analyzed by frame-by-frame replay of the video records. Rating scales of stepping behavior indicated that the hemi-Parkinson rats were chronically impaired in their posture and in the use of the limbs contralateral to the DA-depletion. The contralateral limbs not only displayed postural and movement abnormalities, they participated less in initiating and sustaining propulsion than did the ipsilateral limbs. These findings not only reveal new deficits secondary to unilateral DA-depletion, but also show that the rotorod can provide a robust tool for the qualitative analysis of movement.

Acute Alcohol Administration Improves Skilled Reaching Success in Intact but Not 6-OHDA Dopamine Depleted Rats: a Subsystems Analysis of the Motoric and Anxiolytic Effects of Alcohol

Behavioural Brain Research. Jun, 2003  |  Pubmed ID: 12798278

Low doses of alcohol impair movement and reduce anxiety. Most assessments of movement under ethyl alcohol (alcohol) in the rat have been tests of whole body movements, however. There has been no examination of the effects of alcohol on skilled limb movements, such as reaching for food with a forelimb. This was the purpose of the present study. Rats were trained to reach through a slot of a box with a forelimb in order to obtain a food pellet located on an external shelf. Once asymptotic performance was achieved, rats were given alcohol (20 ml of 8, 12 or 20% (v/v) solution) in separate tests to establish a relationship between alcohol ingestion and skilled reaching performance. Acute treatment with all doses of alcohol impaired postural support, but doses of 8 and 12% alcohol improved skilled reaching success. Qualitative analysis of the movements used for reaching at doses of 8 and 12% indicated that some limb components of the reaching movement were also impaired, perhaps secondarily due to impaired posture. In contrast, the reaching success of rats with unilateral dopamine depletion, induced with the neurotoxin 6-hydroxydopamine (6-OHDA) in the nigrostriatal bundle, was impaired by the same dose of alcohol that improved reaching success in control rats. The finding of improved success in reaching associated with reduced postural support in normal rats suggests a differential action of alcohol on movement subsystems underlying posture relative to skilled movement that depends upon an intact dopaminergic system. The results are also discussed with respect to the relationship of subsystems of movement and anxiety.

Odor Tracking in Rats with Orbital Frontal Lesions

Behavioral Neuroscience. Jun, 2003  |  Pubmed ID: 12802889

Rats track self-, conspecific, and artificial odors to locate food. The orbital frontal cortex has been implicated in olfactory behavior, but whether it plays a role in a species-typical behavior, such as odor-guided navigation, has not been studied. Rats were trained to track 1 of 3 different odors deposited on a string. After rats were reliably tracking a scented string, they received a series of 2- and 3-odor discrimination tests. Next, all the rats received bilateral aspiration lesions of the orbital frontal cortex and experienced the same sequence of tasks. Rats learned to track and discriminate between different odors reliably. These results suggest that other areas of the brain mediate odor-guided navigation following damage to the orbital frontal cortex.

NMDA Lesions of Ammon's Horn and the Dentate Gyrus Disrupt the Direct and Temporally Paced Homing Displayed by Rats Exploring a Novel Environment: Evidence for a Role of the Hippocampus in Dead Reckoning

The European Journal of Neuroscience. Aug, 2003  |  Pubmed ID: 12911747

Dead reckoning, a form of navigation used to locate a present position and to return to a starting position, is used by rats to return to their home base. The present experiment examined whether dead reckoning is displayed by rats during their first exploratory excursions in a novel environment and also examined whether the behaviour requires the integrity of the cells of the hippocampus. Experimental rats, those with NMDA (N-methyl d-aspartate) lesions of Ammon's horn and the dentate gyrus, and control rats could leave a cage to explore a large circular table under light and dark conditions. Home base behaviour, use of olfactory cues, and thigmotaxic- based navigation were evaluated. Temporal, topographical and kinematic analyses were conducted on the first three exploratory excursions that extended at least halfway across the table. Groups did not differ in numbers of exits from the home base, lingering near the home base, distance travelled, or the use of surface cues as might be exemplified by thigmotaxic and olfactory behaviour. Temporal, topographical and kinematic reconstructions of homing behaviour, however, indicated that control rats, but not hippocampal rats, made direct high velocity return trips to the home base in both the light and the dark. Peak velocity of the trips occurred at the trip midpoint, independent of trip distance, suggesting the movements were preplanned. These results are discussed in relation to the ideas that dead reckoning is used in the homing of exploring rats and that this form of navigation involves the hippocampus.

Long-Evans and Sprague-Dawley Rats Have Similar Skilled Reaching Success and Limb Representations in Motor Cortex but Different Movements: Some Cautionary Insights into the Selection of Rat Strains for Neurobiological Motor Research

Behavioural Brain Research. Oct, 2003  |  Pubmed ID: 14529819

Many rat strains are used for neurobiological studies of nervous system function and behavior. The most widely used strain for studies of the neural basis of movement is the out bred, pigmented Long-Evans strain, while the most widely used strains for the study of movement impairments in neurological disease are out bred albino rats, including Sprague-Dawley rats. Although previous research has indicated that there are strain differences in skilled movements displayed by different rat strains, there has been no explicit comparison of the Long-Evans and Sprague-Dawley strains. This was the purpose of the present study. The rats were video recorded as they learned to reach for single food pellets and the video records were subjected to frame-by-frame analysis. Component movements of reaching were scored using a system derived from Eshkol-Wachman Movement Notation (EWMN). The quality of movements was described using Laban Movement Analysis (LMA). Forelimb representations in motor cortex were defined electrophysiologically. Acquisition scores and success in reaching did not differ between the two strains, nor did the topographical representation of the forelimb in motor cortex. Long-Evans and Sprague-Dawley rats did differ in the movements used for reaching and on the quality of their movements. The movements of Sprague-Dawley rats resembled the movements of Long-Evans rats with motor system injury. That rat strains can show both quantitative and qualitative differences in movement is useful for the understanding of the genetic, neural, and behavioral organization of the motor system. The results are also relevant to the question of appropriateness of particular rat strains for studies of neurological diseases and the effects of albinism on motor behavior, and suggest that some of the most widely used rat strains for neurological investigations may be less than appropriate.

Independent Digit Movements and Precision Grip Patterns in 1-5-month-old Human Infants: Hand-babbling, Including Vacuous then Self-directed Hand and Digit Movements, Precedes Targeted Reaching

Neuropsychologia. 2003  |  Pubmed ID: 14572524

Previous work has described human reflexive grasp patterns in early infancy and visually guided reaching and grasping in late infancy. There has been no examination of hand movements in the intervening period. This was the purpose of the present study. We video recorded the spontaneous hand and digit movements made by alert infants over their first 5 months of age. Over this period, spontaneous hand and digit movements developed from fists to almost continuous, vacuous movements and then to self-directed grasping movements. Amongst the many hand and digit movements observed, four grasping patterns emerged during this period: fists, pre-precision grips associated with numerous digit postures, precision grips including the pincer grasp, and self-directed grasps. The finding that a wide range of independent digit movements and grasp patterns are displayed spontaneously by infants within their first 5 months of age is discussed in relation to the development of the motor system, including the suggestion that direct connections of the pyramidal tract are functional relatively early in infancy. It is also suggested that hand babbling, consisting of first vacuous and then self-directed movements, is preparatory to targeted reaching.

Complete and Partial Lesions of the Pyramidal Tract in the Rat Affect Qualitative Measures of Skilled Movements: Impairment in Fixations As a Model for Clumsy Behavior

Neural Plasticity. 2003  |  Pubmed ID: 14640310

Little is known about prenatal and perinatal brain injury resulting in subsequent clumsy behavior in children. One candidate motor system is the pyramidal tract. The tract traverses the entire central nervous system and, through direct and indirect connections to the brainstem and spinal cord sensory and motor nuclei, is involved in the learning and execution of skilled movements. Here, rats, either naive or pretrained on a number of motor tasks, were assessed for acute and chronic impairments following complete or incomplete pyramidal tract lesions. Postsurgery rats with complete lesions were impaired on the qualitative measures of limb aiming, supination, and posture. Impaired movements require fixations, complementary movements in different body segments. The impairment in fixations was manifest acutely and underwent no improvement with subsequent training/testing. The finding that complete and partial pyramidal tract lesions produce chronic impairment in fixations provides insight for understanding clumsy behavior in humans and its potential remediation via specific training in making fixations.

Did a Change in Sensory Control of Skilled Movements Stimulate the Evolution of the Primate Frontal Cortex?

Behavioural Brain Research. Nov, 2003  |  Pubmed ID: 14643457

The classical view of the evolution of such skilled movements as use of the hand and digits for reaching and grasping posited that these movements had their origin in the primate lineage. The hypothesis was that the permissive influence of adaptations to an arboreal environment led to the evolution and elaboration of these skills. Associated with skilled movements were increases in the size of the frontal lobe, temporal lobe, and cerebellum and the elaboration of new connections between these structures and other cortical regions, the brainstem, and spinal cord. The classical view saw rodents as phylogenetically old and relatively unrelated animals, displaying no skilled movements, and whose normal repertoire of behavior had little dependence on the frontal lobes. Here, evidence is reviewed that shows that the classical view of the origins of skilled movements is incorrect. Skilled movements are phylogenetically old, evolved in relation to food handling, and are especially well developed in rodents. Behavioral evidence also shows that the skilled movements of rodents are dependent upon the function of the frontal cortex. Nevertheless, there are difference in the sensory control of skilled movement in primates and rodents. Skilled movements are largely directed by vision in primates but are directed by hapsis/olfaction in rodents. This difference in sensory control suggests that at a dividing point between primates and rodents, there was a profound behavior/brain transformation. Primates retained the skilled movements exemplified in rodents, but brought these movements under visual control. Correspondingly, along with many other anatomical changes, the primate frontal cortex became relatively larger and move complex under visual influence.

Experience and Cortical Control over the Pubertal Transition to Rougher Play Fighting in Rats

Behavioural Brain Research. Feb, 2004  |  Pubmed ID: 14739011

With the onset of puberty, play fighting in rats decreases in frequency and the tactics of attack and defense that are used are rougher. Previous studies have shown that the changes in the frequency of play and in the use of defensive tactics arise independently of social experience. Furthermore, while the former involves subcortical regulation, the latter depends on cortical mechanisms. In this study, the possible mechanisms regulating the developmental changes in the tactics of attack were examined. Two experiments were conducted using male rats. In the first study, rats reared in isolation from weaning were compared to rats reared in pairs, and were tested in the juvenile and early post-pubertal phases (30 and 60 days postnatally). In the second experiment, rats with their cortex removed shortly after birth were compared to sham-treated controls, and were tested in pairs at both the juvenile and early adult phases (30 and 90 days). Two measures of 'roughness,' derived from previous studies, were measured. Results showed that isolation-reared rats had the typical age-related changes in roughness of attack, whereas decorticated rats failed to show this age-related modulation, maintaining, or even exaggerating, the juvenile-typical pattern of attack. These findings suggest that social experience is not needed for this developmental change to occur, and that an intact cortex is needed to regulate this change in behavior.

The Topography of Three-dimensional Exploration: a New Quantification of Vertical and Horizontal Exploration, Postural Support, and Exploratory Bouts in the Cylinder Test

Behavioural Brain Research. May, 2004  |  Pubmed ID: 15084428

The study of exploratory behavior in confined spaces can provide insights into both the spatial and the motor behavior of animals. In the present study, the behavior of rats placed inside of a cylinder (the cylinder test) for 5 min was examined to uncover: (1) the overall organization of exploratory behavior, (2) pattern of movement on the horizontal surface, (3) pattern of movement on the vertical surface, and (4) supporting and stepping movements. The results show that exploratory behavior is organized into a number of bouts of lateral and vertical scans with each bout ending by movement arrest and face washing. Within bouts, activity consists of alternating horizontal and vertical progressions that vary systematically over the course of a bout. Horizontal progressions consist of head scans, turning, and stepping, and decrease in amplitude across a bout. Vertical progressions consist of rears, head scans, and descent with an amplitude expressed by an inverted-U across bouts. Each horizontal and vertical progression is directed toward a different portion of the cylinder and the direction of lateral movements alternate within progressions and between progressions. For each rat, bouts tended to end in the same location suggesting the establishment of a home base. Eshkol-Wachmann movement analysis indicates that during progressions, the forepaws are mainly used for postural support and follow forequarter movements, while upward, downward, and sideward shifts in body weight are generated from the hind limbs. These findings illustrate that in even brief exploratory tests the three-dimensional exploratory behavior of rats is organized. The results are discussed in relation to the use of the cylinder test for analyzing a number of behaviors including exploration, locomotion, and supporting reactions.

Impaired Place Navigation in Place and Matching-to-place Swimming Pool Tasks Follows Both Retrosplenial Cortex Lesions and Cingulum Bundle Lesions in Rats

Hippocampus. 2004  |  Pubmed ID: 15098727

The retrosplenial (RS) cortex (area 29) and the adjacent cingulum bundle (CG) are components of neural circuits that include the hippocampus. Given the evidence suggesting that the hippocampus plays a central role in spatial navigation, several lines of investigation have examined the possible contributions of these structures to spatial navigation. The combined and/or separate contributions of these structures have been difficult to establish because their close proximity usually results in combined injury after lesions and because there have been conflicting results related to lesion type and the strain of rat subjects. The purpose of the present study was to compare the effects of selective CG damage with selective RS damage in Long-Evans rats, a domestic rat strain that displays superior spatial skills, and by using spatial behavior assessment procedures that are sensitive to CG damage. Rats with cytotoxic N-methyl-D-aspartate (NMDA) RS lesions or surgical CG transection were tested on two spatial tasks in the Morris water task; a place learning task, sensitive to nonspatial and spatial behavior, and a matching-to-place task, sensitive to spatial behavior. Both the RS and CG groups were impaired on most measures relative to the control group on both the place task and the matching-to-place task. The results are discussed in relation to the anatomical organization of CG and RG projections to the hippocampus and with respect to their possible separate/conjoint contributions to spatial behavior.

Precision Grasps of Children and Young and Old Adults: Individual Differences in Digit Contact Strategy, Purchase Pattern, and Digit Posture

Behavioural Brain Research. Sep, 2004  |  Pubmed ID: 15302117

The evolutionary origins and variations of the precision grip, in which an object is held between the thumb and other digits, are poorly understood. This is surprising because the neural basis of this grasp pattern, including the motor cortex and pyramidal tract have received extensive study. Most previous work has shown that features of an object to be grasped (external factors) determine grasp patterns. The objective of the present study was to investigate individual differences (central factors) in use of the pincer and other precision grips. The grasping patterns of male and female young adults, older adults and children were examined as they reached (with both left and right hand) for five small beads (3-16 mm diameter). Frame-by-frame analysis of grasping indicated a high degree of variability in digit contact strategies, purchase patterns and digit posture both within and between subjects. (1) The contact strategies consisted of five variations, depending on whether the thumb or the index finger dragged or stabilized the bead for grasping. (2) Purchase patterns consisted of seven different types of precision grips, involving the thumb and various combinations of other digits. (3) There were four variations stemming from the posture of the non-grasping digits. Grip patterns of the left and right hands were correlated in individual subjects, as were strategies used for different bead sizes. Females displayed slightly more variability in grasp patterns than did males, and digit width (obtained from photocopies of the subjects' hands) was weakly correlated with the grasp patterns used. Although it was expected that the pincer would be used for all objects, it was preferentially used for only the smallest object except for older adults who used the pincer grasp on most objects. The variability in digit contact strategies, purchase patterns, and posture of the non-grasping digits indicates that central factors (innate or learning-induced architecture of the left parietal cortex) make important contributions to the selection of a grasping pattern. These individual differences are discussed in relation to the neural control of grasping and its potential contribution to understanding the evolution, development, and pathology of the precision grip.

Sequential Control of Navigation by Locale and Taxon Cues in the Morris Water Task

Behavioural Brain Research. Oct, 2004  |  Pubmed ID: 15313026

The neurobehavioral dissociation between place navigation and cued navigation has been central to contemporary thinking regarding the psychological processes involved in spatial behavior. In cases where locale (place) cues and taxon cues (e.g., beacons) are present it has been suggested that navigation may be controlled by either stimulus type in isolation, or, alternatively, by both simultaneously. In this report we provide evidence that place cues and beacons sequentially control navigation during a single trip to a visible goal. Rats were trained to navigate to a visible escape platform in a circular swimming pool surrounded by numerous visual cues and the kinematics and accuracy of the trajectories to the platform were analyzed. Shortly after initiating a trajectory to the visible platform, animals routinely engaged in stimulus sampling behaviors (e.g., horizontal head scans) which were consistently associated with changes in accuracy (heading error) and swim velocity. Subsequently, animals swam quickly and accurately to the visible platform suggesting that the sampling behaviors correspond to a shift in exteroceptive stimulus control. Consistent with this idea, removal or relocation of the platform disrupted navigation following the stimulus sampling behaviors, whereas the initial trajectory was unaffected. In contrast, changes in the distal cue constellation selectively disrupted the initial trajectory. The results showing that navigation to a visible goal is controlled sequentially by locale and taxon cues are discussed in relation to contemporary theories of navigation.

Posterior Neocortical (visual Cortex) Lesions in the Rat Impair Matching-to-place Navigation in a Swimming Pool: a Reevaluation of Cortical Contributions to Spatial Behavior Using a New Assessment of Spatial Versus Nonspatial Behavior

Behavioural Brain Research. Nov, 2004  |  Pubmed ID: 15325784

In the face of contradictory findings on the role of visual cortex contributions to spatial behavior, the present study evaluated the ability of rats with primary visual cortex (area 17) lesions to learn spatial problems in a swimming pool. Because the solution to any spatial learning problem consists of acquiring at least two primary elements of a task, task procedures and spatial learning, the study, in addition to assessing spatial ability on a place task, used two training/testing methods to identify the nature of the spatial impairment associated with visual cortex lesions. Non-spatial training consisted of learning to find a platform in the dark and spatial training consisted of a series of matching-to-place problems. The results confirmed that although rats with visual cortex lesions were impaired on place learning, the deficit was partially ameliorated by non-spatial training given following the lesion, and completely ameliorated by non-spatial training given before the lesion. Nevertheless, all visual cortex groups failed to show a quadrant preference on a probe trial and displayed a profound impairment in matching-to-place learning. This definitive demonstration that appropriate testing methods can reveal a failure in spatial behavior following visual cortex lesions is consistent with the idea that primary visual cortex is required in spatial navigation.

Posterior Neocortical (visual Cortex) Lesions in the Rat Impair Matching-to-place Navigation in a Swimming Pool: a Reevaluation of Cortical Contributions to Spatial Behavior Using a New Assessment of Spatial Versus Non-spatial Behavior

Behavioural Brain Research. Dec, 2004  |  Pubmed ID: 15364476

In the face of contradictory findings on the role of visual cortex contributions to spatial behavior, the present study evaluated the ability of rats with primary visual cortex (Area 17) lesions to learn spatial problems in a swimming pool. Because the solution to any spatial learning problem consists of acquiring at least two primary elements of a task, task procedures and spatial learning, the study, in addition to assessing spatial ability on a place task, used two training/testing methods to identify the nature of the spatial impairment associated with visual cortex lesions. Non-spatial training consisted of learning to find a platform in the dark and spatial training consisted of a series of matching-to-place problems. The results confirmed that although rats with visual cortex lesions were impaired on place learning, the deficit was partially ameliorated by non-spatial training given following the lesion, and completely ameliorated by non-spatial training given before the lesion. Nevertheless, all visual cortex groups failed to show a quadrant preference on a probe trial and displayed a profound impairment in matching-to-place learning. This definitive demonstration that appropriate testing methods can reveal a failure in spatial behavior following visual cortex lesions is consistent with the idea that primary visual cortex is required in spatial navigation.

A Reaffirmation of the Retrosplenial Contribution to Rodent Navigation: Reviewing the Influences of Lesion, Strain, and Task

Neuroscience and Biobehavioral Reviews. Sep, 2004  |  Pubmed ID: 15465136

Retrosplenial cortex (RS) is situated both anatomically and functionally between neocortical and limbic structures involved in spatial navigation. Initial anatomical, electrophysiological and behavioural evidence in both humans and rodents strongly suggested a role for RS in spatial navigation as well. Later studies using more selective cytotoxic lesions in rodents, however, cast doubt on earlier RS studies by failing to find spatial deficits following RS lesions. Contrasting reports from behavioural results on spatial tasks following RS damage have continued to be reported during the past decade. That RS does indeed contribute spatial behaviour even in rodents has been recently reaffirmed. The ambiguity surrounding RS is shown to result from differences in the choice of spatial tasks and rat strains between studies that find RS deficits and those that do not. The reconciliation of behavioural results following RS lesions strengthens the view that RS forms a part of the neural circuitry that underlies spatial navigation.

Unilateral Frontal Lobe Contusion and Forelimb Function: Chronic Quantitative and Qualitative Impairments in Reflexive and Skilled Forelimb Movements in Rats

Journal of Neurotrauma. Nov, 2004  |  Pubmed ID: 15684651

Traumatic brain injury induced by mechanical impacts of the head can be modeled in rats in order to investigate acute and chronic therapy. Because frontal lobe contusion affects the neural representation of the forelimb in both the neocortex and basal ganglia, the purpose of the present experiments was to examine the chronic changes in reflexive and skilled forelimb induced by the injury. Contusions produced a cavity in the sensorimotor cortex, accompanied by shrinkage of the pyramidal tract, loss of cells in the dorsolateral striatum, and enlargement of the lateral ventricle. There were substantial individual differences in lesion size despite use of two different contusion forces, but all rats receiving contusions displayed chronic forelimb deficits. Reflexive tests of forelimb use (limb posture, placing, and support) indicated that impairments were most pronounced in the forelimb contralateral to the lesion. Tests of limb preference indicated that the contusion rats displayed a forelimb asymmetry: they were more likely to lean on their ipsilateral-to-lesion forelimb for support when rearing in a test cylinder, and this impairment was amplified in a home cage test. They also displayed a preference for the forelimb ipsilateral to the lesion when reaching for food, although both forelimbs were equally impaired on measures of success when reaching for food from a tray and reaching for a single food pellet on a shelf. A qualitative analysis from frame-by-frame video records indicated that when reaching for single pellets, impairments in forelimb use primarily affected the contralateral-to-lesion limb, especially limb aiming, supination, and food pellet release. Impairments in the ipsilateral-to-lesion forelimb were generally, but not exclusively, secondary to postural abnormalities. The wide range of chronic impairments in forelimb use following contusion injuries are discussed in relation to the anatomical and behavioral origins of the impairments and the potential use of forelimb tests in the assessment of therapy for traumatic brain injury to the frontal cortex.

Preserved Ipsilateral-to-lesion Motor Map Organization in the Unilateral 6-OHDA-treated Rat Model of Parkinson's Disease

Brain Research. Nov, 2004  |  Pubmed ID: 15476704

The classic view of dopamine (DA) loss in Parkinson's disease is that it produces a functional deafferentation in striatal-cortical circuitry that, in turn, contributes to sensorimotor deficits. The present study examines this view in the rat by assessing how DA-depletion affects the intracortical microstimulation (ICMS) topographic representation of movement in the rostral and caudal motor areas of the motor cortex. The ICMS map is used as an index of motor cortex function because it has been shown to reflect motor function and experience. Groups of rats received no training or skilled reach training and were then given unilateral 6-hydroxydopamine (6-OHDA) or sham lesions of the nigrostriatal bundle to deplete nigrostriatal DA. Lesion success was confirmed by abnormalities in skilled reaching, by apomorphine-induced rotation, and by loss of DA neurons in the substantia nigra. The size and threshold of the motor map in naive and skilled reach trained DA-depleted rats were preserved. In addition, there was an increase in distal limb representation in the caudal forelimb area (CFA) in the DA-depleted rats suggesting a possible plastic response to the behavioral effects of DA-depletion. The presence of preserved size and modified map organization in DA-depleted rats is discussed in relation to the hypothesis that preserved motor cortex functionality despite DA loss underlies the spared motor abilities of DA-depleted rats.

Anesthetized Long Evans Rats Show Similar Protein Expression and Long-term Potentiation As Fischer 344 Rats but Reduced Short-term Potentiation in Motor Cortex

Brain Research. Dec, 2004  |  Pubmed ID: 15533310

A number of studies describe strain-related differences in the motor behavior of rats. Inbred albino F344 rats are found to be impaired in procedural spatial learning, skilled reaching, and over ground locomotion in relation to pigmented out bred Long Evans (LE) rats. These deficits could be related to the functional differences in the motor cortex of the two strains, and the objective of the present study was to examine this hypothesis. Synaptic transmission was examined in the two rat strains, using long-term potentiation (LTP) and short-term potentiation (STP), two electrophysiological measures of neural function and learning. Field potentials were evoked in the motor cortex of anesthetized Long Evans and Fischer 344 (F344) rats in response to contralateral white matter stimulation. The main findings indicated that (1) baseline-evoked responses in the two strains was similar, indicating similar basal levels of synaptic strength, (2) LTP was induced in both strains of rats, suggesting similar synaptic efficacy in the two strains of rats, and (3) STP was enhanced in the Fischer 344 rats, suggesting differences in synaptic function. Protein expression also revealed that the two strains did not differ with respect to structural or synaptic protein expression. Thus, the two strains exhibit motor skill differences despite a great degree of physiological similarity in motor cortex. The results are discussed in relation to the greater utility of using the Long Evans rat for examining the neural basis of plasticity and models of disease, especially if motor tasks are evaluated.

Neonatal and Pubertal, but Not Adult, Ovarian Steroids Are Necessary for the Development of Female-typical Patterns of Dodging to Protect a Food Item

Behavioral Neuroscience. Dec, 2004  |  Pubmed ID: 15598138

Rats protect food by dodging horizontally away from a conspecific. Females and males use different movement and stepping patterns to execute a dodge. An unresolved question is whether exposure to ovarian steroids in females is necessary for the development of the female-typical pattern. Females ovariectomized neonatally and prior to puberty use a combination of male and female tactics. Pregnant females, however, use a female-typical pattern of dodging, suggesting that the patterns used by prepubertal ovariectomized females are not due to their increase in body mass. Thus, the contribution of ovarian steroids to the development of female-typical patterns of behavior needs to be studied further at both a behavioral and neural level with regard to the organization of movement.

Evidence for Bilateral Control of Skilled Movements: Ipsilateral Skilled Forelimb Reaching Deficits and Functional Recovery in Rats Follow Motor Cortex and Lateral Frontal Cortex Lesions

The European Journal of Neuroscience. Dec, 2004  |  Pubmed ID: 15610177

Unilateral damage to cortical areas in the frontal cortex produces sensorimotor deficits on the side contralateral to the lesion. Although there are anecdotal reports of bilateral deficits after stroke in humans and in experimental animals, little is known of the effects of unilateral lesions on the same side of the body. The objective of the present study was to make a systematic examination of the motor skills of the ipsilateral forelimb after frontal cortex lesions to either the motor cortex by devascularization of the surface blood vessels (pial stroke), or to the lateral cortex by electrocoagulation of the distal branches of the middle cerebral artery (MCA stroke). Plastic processes in the intact hemisphere were documented using Golgi-Cox dendritic analysis and by intracortical microstimulation analysis. Although tests of reflexive responses in forelimb placing identified a contralateral motor impairment following both cortical lesions, quantitative and qualitative measures of skilled reaching identified a severe ipsilateral impairment from which recovery was substantial but incomplete. Golgi-impregnated pyramidal cells in the forelimb area showed an increase in dendritic length and branching. Electrophysiological mapping showed normal size forelimb representations in the lesioned rats relative to control animals. The finding of an enduring ipsilateral impairment in skilled movement is consistent with a large but more anecdotal literature in rats, nonhuman primates and humans, and suggests that plastic changes in the intact hemisphere are related to that hemisphere's contribution to skilled movement.

Nicotine Stimulates Dendritic Arborization in Motor Cortex and Improves Concurrent Motor Skill but Impairs Subsequent Motor Learning

Synapse (New York, N.Y.). Mar, 2005  |  Pubmed ID: 15635590

The effect of the premature commitment of neurons to exuberant growth by nicotine on concurrent and subsequent learning is unknown and was the focus of the present study. Animals were trained on a tray reaching for food task (where lots of pieces of chicken feed were available) for 3 weeks before they received two daily injections of nicotine (0.3 mg/kg) or 0.9% saline for 12 days. Measures of tray-reaching performance were obtained before the administration of nicotine and every other week for a total of 7 weeks. Starting on week 8, animals were given a novel motor skill problem that required them to learn to use a forepaw to reach through a slot in a cage for single food pellets located on an external shelf. Pyramidal cells in the forelimb area of both hemispheres were then examined for dendritic length and branching using a Golgi-Cox procedure. Animals treated with saline displayed excellent performance in both reaching tasks and an increase in neuronal branching in Layer V pyramidal cells in the motor cortex contralateral to the reaching paw. In contrast, animals treated with nicotine showed bilateral increases in neuronal branching. Behavioral results showed that nicotine improved forelimb use in the concurrently administered tray-reaching task, but severely degraded quantitative and qualitative scores of skilled forelimb use in the subsequently administered single-pellet reaching task. The results suggest that plasticity coincidence with skilled training is essential to skilled motor learning, but this expenditure can impair subsequent learning.

A Masculinized Skeletomusculature is Not Necessary for Male-typical Patterns of Food-protective Movement

Hormones and Behavior. Jan, 2005  |  Pubmed ID: 15579265

Although sexual dimorphism in movement has been documented in rodents, the extent to which it relates to dimorphic neural control versus dimorphic body size/structure is unclear. We have shown previously that male and female rats are sexually dimorphic with regards to the lateral movements and hindpaw stepping they use to protect a food item. We addressed the question of whether this sexual dimorphism is due to sex differences in peripheral skeletomusculature or in the CNS by examining the movement composition used during dodging to protect a food item by tfm-affected males and their wild-type male (WTM) and female (WTF) controls. The tfm-affected male, while genetically male, develops internal testes that secrete testosterone, but is phenotypically female due to a failure of androgen receptor-mediated masculinization of the periphery. Masculinization of the CNS of tfm-affected males, however, is primarily accomplished by the actions of testosterone's aromatized metabolite estradiol acting via estrogen receptors. Thus the tfm-affected male provides an assay by which the relative contributions of the skeletomusculature or CNS to sex differences in movement organization can be addressed. We found that female wild-type animals were significantly different from both the tfm-affected and wild-type males. There were no significant differences in dodge patterns used by tfm-affected males and their wild-type male controls. This study provides evidence that the sex differences in dodging patterns are mediated primarily by CNS mechanisms and are not primarily dependent on a male- or female-typical skeletomusculature.

The Development of Spatial Capacity in Piloting and Dead Reckoning by Infant Rats: Use of the Huddle As a Home Base for Spatial Navigation

Developmental Psychobiology. May, 2005  |  Pubmed ID: 15832318

Two forms of spatial navigation, piloting using external cues and dead reckoning using self-movement cues, are manifest in the outward and homeward trips of adult rats exploring from a home base. Here, the development of these two forms of spatial behavior are described for rats aged 14-65 days using a new paradigm in which a huddle of pups or an artificial huddle, a small heat pad, served as a home base on an open circular table that the rats could explore. When moving away from both home bases, the travel distance, path complexity, and number of stops of outward trips from the home base increased progressively with age from postnatal day 16 through 22. When returning to the home bases, the return trips to the home base were always more direct and had high travel velocities even though travel distance increased with age for the longest trips. The results are discussed in relation to the ideas that: (1) the pups pilot on the outward portion of their excursion and dead reckon on the homeward portion of their excursion, and (2) the two forms of navigation and associated spatial capacity are interdependent and develop in parallel and in close association with locomotor skill.

Pallidal Deep Brain Stimulation and L-dopa Do Not Improve Qualitative Aspects of Skilled Reaching in Parkinson's Disease

Behavioural Brain Research. May, 2005  |  Pubmed ID: 15836914

To determine effects of dopaminergic medication and pallidal deep brain stimulation (DBS) on skilled reach in Parkinson's disease (PD).

Movements of Exploration Intact in Rats with Hippocampal Lesions

Behavioural Brain Research. Aug, 2005  |  Pubmed ID: 15904983

Prompted by the theoretical prediction that damage to the hippocampus should abolish exploratory behavior, the present study examined exploratory movements in control rats and rats with hippocampal lesions produced with the neurotoxin N-methyl d-aspartate (NMDA). In four daily 30-min sessions, control and hippocampal rats were exposed to an open circular table under room lighting. Both control and hippocampal rats spent a majority of time near, and organized trips away from, a portion of the table (home base) near a large cue placed proximal to the table. On Day 1, control and HPC rats made equal numbers of head orientations and a comparable number of trips, featuring equal travel distance and numbers of stops. By Day 4, dwell times near the home base increased and other movements decreased in the control rats but the activity profile of Day 1 persisted in the hippocampal rats. The high degree of similarity in behavior between hippocampal and control rats on Day 1 and the persistence of this behavior in hippocampal rats on Day 4 suggests that the hippocampus is not necessary for the display of normal exploratory movements per se. The absence of habituation of exploration in hippocampal rats is discussed in relation to contemporary theories of hippocampal function.

Sexually Dimorphic Postural Adjustments Are Used in a Skilled Reaching Task in the Rat

Behavioural Brain Research. Sep, 2005  |  Pubmed ID: 16023226

Sex differences occur not only in the sexual repertoire of animals but also are evident in other aspects of movement. The present study asked whether sexually dimorphic motor behavior extends to the skilled movements used in reaching for food in the rat. Because we have previously shown that males and females are sexually dimorphic in their organization of lateral and rotatory movements and because postural adjustments are incorporated into skilled movements, both body posture and limb movements were examined during a skilled reaching task. Male and female Long-Evans rats were filmed, from both the front and ventral views and their stepping patterns, postural adjustments and forelimb movements, during a successful reach were analyzed. While males and females did not differ in forelimb movements, they were significantly different in how they approached and oriented their body to the food item during a successful reach. These results are discussed in relation to the dissociation of skilled movement from postural adjustments, sex-dependent alterations following CNS injury, and the neural and evolutionary basis of sex differences in movement organization.

Limits on Recovery in the Corticospinal Tract of the Rat: Partial Lesions Impair Skilled Reaching and the Topographic Representation of the Forelimb in Motor Cortex

Brain Research Bulletin. Aug, 2005  |  Pubmed ID: 16023917

Although evidence suggests that there are impairments in skilled movements following very large lesions of the pyramidal component of the corticospinal tract, the behavioral and electrophysiological effects of partial lesion has not received equal attention. Here, rats with complete lesions or partial lesions (medial, central, or lateral third) of the pyramidal tract at the medullary pyramids were evaluated for their quantitative and qualitative postsurgical performance on a skilled reaching task, following which the topographic representation of their forelimb was mapped with intracortical microstimulation (ICMS). Complete lesions impaired reaching success, impaired the qualitative features of reaching movements, and abolished ICMS evoked movement from the forelimb region of motor cortex. Although partial lesions did not impair reaching success, they did impair qualitative aspects of limb movement including forepaw aiming, supination, and food pellet release. ICMS indicated a reduction in the size of the forelimb area, especially the distal area of the caudal forelimb area (CFA), of the motor map. The behavioral and electrophysiological impairments did not vary with lesion location within the pyramidal tract. The incomplete recovery, as measured both behaviorally and electrophysiologically, demonstrates that plasticity within the corticospinal system is limited even with lesions that permit substantial sparing of pyramidal tract fibers.

Home Bases Formed to Visual Cues but Not to Self-movement (dead Reckoning) Cues in Exploring Hippocampectomized Rats

The European Journal of Neuroscience. Nov, 2005  |  Pubmed ID: 16262675

Spatial theory proposes that the hippocampus contributes to exploratory behavior allowing animals to acquire information about their environment. In the present study, the exploratory movements of control rats, bulbectomized (anosmic) rats and hippocampectomized rats using the neurotoxin N-methyl-D-aspartate (NMDA) were monitored on a large circular table without walls and around which visual cues were manipulated. The rats displayed organized spatial behavior in that they developed home bases, one or more places operationally defined as those in which they spent a preponderance of time, in which they moved slowly, and to which they returned after excursions. Control rats and hippocampectomized rats were similar in that they established home bases: (i) adjacent to a proximal stable or moving visual landmark; (ii) in relation to more distant visual room cues; and (iii) in relation to contextually conditioned visual cues. Nevertheless, in exploratory tests given under infrared light, a wavelength to which rats are insensitive, control rats and bulbectomized rats established one or more home bases that were not dependent upon surface (e.g. olfactory) cues, whereas home base behavior was absent/fragmented in hippocampectomized rats. Thus, exploratory behavior, as exemplified by home base behavior, is organized in control and hippocampectomized rats in relation to visual cues, but is not organized in hippocampectomized rats when visual cues are absent. This result is discussed in relation to the idea that the hippocampus contributes to spatial behavior that is dependent upon guidance (dead reckoning) derived from self-movement cues.

Skilled Reaching Impairments from the Lateral Frontal Cortex Component of Middle Cerebral Artery Stroke: a Qualitative and Quantitative Comparison to Focal Motor Cortex Lesions in Rats

Behavioural Brain Research. Jan, 2005  |  Pubmed ID: 15474657

The classical approach to investigating brain contributions to behavior has been to localize function to a region. In clinical investigations, however, injury is frequently multifocal, raising the question of how individual brain regions contribute to a resulting behavioral syndrome. For example, middle cerebral artery (MCA) ischemia in humans can concurrently damage a number of cortical and subcortical areas and the same areas are damaged in rat models of MCA stroke. In the rat, MCA occlusion produces severe motor deficits, but the cortical area of damage is the lateral neocortex, sparing motor cortex. This anatomical finding raises the question of whether the rat lateral neocortex contributes to MCA-related motor impairments, a question that was investigated in the present study. Rats received unilateral neocortical lesions via electrocoagulation of the MCA and were compared to rats with standard motor cortex lesions produced by devascaulrization of the overlaying blood vessels. The MCA group was as impaired as the motor cortex group in skilled reaching movements as assessed by quantitative measures of the contralateral-to-lesion forelimb in a single pellet task and in a tray-reaching task. Although there was improvement in success scores over a 2-week period in both groups, the groups were characterized by distinctive and enduring qualitative impairments. The motor cortex deficit was exemplified by use of trunk musculature and head movements to assist the reaching limb while the MCA impairment included sensory abnormalities. The results are discussed in relation to the contribution of lateral frontal cortex injury to MCA stroke sensorimotor syndromes.

Bilateral Alteration in Stepping Pattern After Unilateral Motor Cortex Injury: a New Test Strategy for Analysis of Skilled Limb Movements in Neurological Mouse Models

Journal of Neuroscience Methods. May, 2006  |  Pubmed ID: 16309746

Mice are becoming increasingly popular to model neurological disease and motor system dysfunction. For evaluation of discrete, chronic motor impairments, skilled limb movements represent a valuable extension of standard mouse test batteries. This study introduces an efficient and sensitive test strategy for comprehensive assessment of skilled fore- and hind-limb stepping in mice. Adult C57BL/6 mice were trained and video-recorded in two walking tasks, the widely used rotorod test and a new ladder rung task. The animals then received a unilateral ischemic lesion in the motor cortex forelimb and hind limb area and were video-recorded on days 12 and 26 post-lesion. Forelimb and hind limb stepping movements were rated using a combination of endpoint measures and qualitative assessment. The results showed that while animals maintained a weight-supported gait, posture and stepping movements were abnormal at both post-operative intervals. The rotorod analysis revealed stepping deficits in both forelimbs that led to adoption of compensatory movement strategies. The ladder rung task revealed stepping errors in ipsi- and contralateral fore- and hind-limbs. The findings demonstrate that this test strategy provides comprehensive assessment of motor impairments in mice and that qualitative movement analysis is a valuable tool for elaborating subtle motor disturbances.

Motor Deficits in Parkinsonian Reaching: Dopa-sensitivity Influenced by Real-world Task Constraint

Journal of Motor Behavior. Jan, 2006  |  Pubmed ID: 16436362

Parkinson's disease (PD) patients can perform many daily activities, but movement deficits are evident. Those deficits may be increased when the required movement is constrained in accuracy. Variable improvements in performance with PD medication have been demonstrated, and sensitivity to task constraint has been evident in some studies. The authors quantified both specific movement deficits and improvements for PD patients in a reaching task. PD patients (N=8) both on and off medication showed a need for greater ongoing control in movements with higher task-accuracy constraints. Increased task-accuracy constraints further compromised movement timing and structure among PD patients who were off medication, suggesting that unmedicated PD patients may typically compensate by using more conscious control of movement, resulting in increased slowing and segmentation of components when higher task accuracy is required.

Play Fighting in Androgen-insensitive Tfm Rats: Evidence That Androgen Receptors Are Necessary for the Development of Adult Playful Attack and Defense

Developmental Psychobiology. Mar, 2006  |  Pubmed ID: 16489596

The frequency of playful attack and the style of playful defense, are modifiable by gonadal steroids and change after puberty in male and female rats. The present study examined the play behavior exhibited by testicular feminized mutation (tfm)-affected males, who are insensitive to androgens but can bind estrogens aromatized from androgens, to determine the relative contributions of androgens and estrogens to the age-related changes in play behavior. tfm males did not exhibit a decrease in playful attack with age and were more likely to maintain the use of complete rotations, a juvenile form of playful defense, into adulthood. tfm males did however, show age related changes in the use of partial rotations and upright postures, two other forms of playful defense, that were similar to normal males. These data suggest that the development of play fighting and defense in males is dependent on both androgen- and estrogen-receptor-mediated effects.

Motor Activity (exploration) and Formation of Home Bases in Mice (C57BL/6) Influenced by Visual and Tactile Cues: Modification of Movement Distribution, Distance, Location, and Speed

Physiology & Behavior. Apr, 2006  |  Pubmed ID: 16530235

The motor activity of mice in tests of "exploration" is organized. Mice establish home bases, operationally defined as places where they spend long periods of time, near physical objects and nesting material from which they make excursions. This organization raises the question of the extent to which mouse motoric activity is modulated by innate predispositions versus environmental influences. Here the influence of contextual cues (visual and tactile) on the motor activity of C57BL/6 mice was examined: (1) on an open field that had no walls, a partial wall, or a complete wall, (2) in the presence of distinct visual cues, room cues, or in the absence of visual cues (infrared light), and (3) in the presence of configurations of visual and tactile cues. Mice were generally less active in the presence of salient cues and formed home bases near those cues. In addition, movement speed, path distribution, and the number and length of stops were modulated by contextual cues. With repeated tests, mice favored tactile cues over visual cues as their home base locations. Although responses to cues were robust over test days, conditioning to context was generally weak. That the exploratory behavior of mice is affected by experience and context provides insights into performance variability and may prove useful in investigating the genetic and neural influences on mouse behavior.

The Exploratory Behavior of Rats in an Open Environment Optimizes Security

Behavioural Brain Research. Aug, 2006  |  Pubmed ID: 16678279

When given a locomotor/exploratory test in the laboratory, rats form one or more home bases, operationally defined as places where they spend a disproportionate period of their time and from which they make excursions. Because exploratory tests in the laboratory necessarily restrict the animals' movements, the cause of exploration (e.g., fear, curiosity, innate disposition) and the extent to which organization is imposed by the restriction of the testing environment has not been fully examined. In the present study, rats received exploratory tests in environments in which restrictions were remote; in a parking lot or on a playing field. Each rat began a test in one of three conditions: in a small refuge, within a transparent open home cage, or beside a landmark. In the parking lot, the rats failed to leave the small refuge, made excursions from the home cage, and left the landmark, usually at a gallop, and made no movements of returning. On the playing field they remained in the small refuge, left and returned to the open home cage, and were more likely to permanently leave the landmark at a gallop. Rats that displayed a strong preference for the landmark over three test sessions in a laboratory, also immediately left the same landmark when tested on the playing field. The pattern of behavior, in which the rats failed to explore from a secure starting position and were increasingly likely to run away as security decreased, suggests that a primary function of locomotor behavior in a novel environment is to optimize security. The results are discussed in relation to the advantages of investigating the influence of neural processes on exploration in terms optimization theory versus motivational theory.

Parkinsonian Deficits in Sensory Integration for Postural Control: Temporal Response to Changes in Visual Input

Parkinsonism & Related Disorders. Sep, 2006  |  Pubmed ID: 16720099

This study investigated the effect of Parkinson's disease (PD) on the time course for postural control following the removal and reinsertion of visual information. Twelve medicated PD patients (PD) and 12 age matched control (CTRL) subjects performed two 45-s quiet standing trials, during which visual feedback was available (0-15s), deprived (15-30s), and then restored (30-45s). The 45s test trial was divided into 5s time bins to compare the time-based effect of sensory reorganization during deprivation and reintegration. Results revealed an increase in Elliptical Sway Area (ESA) following visual deprivation for both groups; this increased ESA remained significantly higher than the baseline level for the duration of the deprivation period among PD patients and returned to baseline the level among CTRL. Despite elevated ESA at the end of visual deprivation among PD patients, neither group showed a change in ESA after visual information was restored. These results indicate a PD-associated deficit with the reorganization of sensory priorities for postural control, and may implicate the basal ganglia as being critical for integration of sensory information for postural control.

Changes in the Kinematic Structure and Non-kinematic Features of Movements During Skilled Reaching After Stroke: a Laban Movement Analysis in Two Case Studies

Journal of Neuroscience Methods. Nov, 2006  |  Pubmed ID: 16766042

The purpose of this study was to adapt a universal language for human movement, Laban Movement Analysis (LMA), to capture the kinematic and non-kinematic aspects of movement in a reach-for-food task by subjects whose movements had been affected by stroke. Two control subjects, one stroke subject with internal capsule damage, and one subject with right posterior parietal stroke were video recorded while performing the reaching task. The movements of limb advancement, grasping the food, and limb withdrawal to place the food in the mouth, were notated using LMA. A scale, the Expressive Reaching Scale (ERS), was derived from the notation. All subjects completed the task; however, the stroke subjects displayed abnormalities in both the kinematic and non-kinematic aspects of movements during reaching with either limb. The most extensive impairments were in the contralateral-to-stroke limb and were most severe in the subject with internal capsule damage. The ERS rating scale may be a useful diagnosis and assessment tool.

Movement Characteristics Support a Role for Dead Reckoning in Organizing Exploratory Behavior

Animal Cognition. Jul, 2006  |  Pubmed ID: 16767471

Rat exploration is an organized series of trips. Each exploratory trip involves an outward tour from the refuge followed by a return to the refuge. A tour consists of a sequence of progressions with variable direction and speed concatenated by stops, whereas the return consists of a single direct progression. We have argued that processing self-movement information generated on the tour allows a rat to plot the return to the refuge. This claim has been supported by observing consistent differences between tour and return segments independent of ambient cue availability; however, this distinction was based on differences in movement characteristics derived from multiple progressions and stops on the tour and the single progression on the return. The present study examines movement characteristics of the tour and return progressions under novel-dark and light conditions. Three novel characteristics of progressions were identified: (1) linear speeds and path curvature of exploratory trips are negatively correlated, (2) tour progression maximum linear speed and temporal pacing varies as a function of travel distance, and (3) return progression movement characteristics are qualitatively different from tour progressions of comparable length. These observations support a role for dead reckoning in organizing exploratory behavior.

Pharmacological Manipulations of Food Protection Behavior in Rats: Evidence for Dopaminergic Contributions to Time Perception During a Natural Behavior

Brain Research. Sep, 2006  |  Pubmed ID: 16890923

Operant procedures combined with pharmacological manipulations have implicated a role for the dopaminergic system in the perception and production of temporal intervals. Because studies have suggested that animals use temporal information to organize food protection behavior, the current study investigates whether dopaminergic systems are involved in timing during this natural behavior. The experiment examined the influence of a dopaminergic agonist (amphetamine) and an antagonist (haloperidol) on food protection behavior initiated to avoid theft by a conspecific. Amphetamine increased the time spent dodging and decreased the time spent bracing during the consumption of a hazelnut. On the other hand, haloperidol decreased the time spent dodging while showing no systematic changes in bracing. Topographic and kinematic analyses of rat movement conflicted with motivational, motoric, and social accounts of drug-induced changes in food protection behavior organization. These observations provide evidence that rats use temporal information to organize movements in the natural behavior of protecting food from theft by a conspecific, and this organization is influenced by both a dopaminergic agonist and an antagonist.

Sexually Dimorphic Postural Adjustments During Vertical Behaviour Are Altered in a Unilateral 6-OHDA Rat Model of Parkinson's Disease

Behavioural Brain Research. Nov, 2006  |  Pubmed ID: 16930735

The study of sex differences in the onset, progression and symptoms of Parkinson's disease, in humans, has led to mixed results. In this study, we used a unilateral 6-hydroxydopamine (6-OHDA) lesion animal model of Parkinson's disease, to address whether there are sex differences in the composition of the movements used during vertical exploration within a confined cylinder. Tyrosine hydroxylase staining and apomorphine induced rotation were used to confirm lesion magnitude. There were no sex differences or lesion effects in the frequency of occurrence of a vertical bout or the average time spent vertical. Both male and female 6-OHDA animals exhibited equal impairments in the use of the forelimbs during vertical exploration. 6-OHDA males, as compared to 6-OHDA females, however, had a significant reduction in the use of their hindlimbs. An analysis of hindlimb step direction revealed that while sham females were more likely to step forward, sham males were more likely to step backwards during a vertical bout. This sex difference was no longer present in the 6-OHDA animals. Finally, 6-OHDA males were significantly more likely to place their dorsal surface in contact with the wall of the cylinder to maintain an upright posture during a vertical bout than animals in any other condition. These results demonstrate that the use of a confined cylinder task is appropriate for the kinematic analysis of sex differences in vertical behaviour and show that there are sex differences in motor behaviour in an animal model of human Parkinson's disease.

Parallel Stages of Learning and Recovery of Skilled Reaching After Motor Cortex Stroke: "oppositions" Organize Normal and Compensatory Movements

Behavioural Brain Research. Dec, 2006  |  Pubmed ID: 17049628

Forelimb/hand motor cortex injury in rodents and primates causes impairments in skilled paw/hand movements that includes a period of movement absence followed by functional recovery/compensation. Although the postsurgical period of movement absence has been attributed to "shock" or "diaschisis", the behavior of animals during this period has not been fully described. Here, rats were trained to reach for single food pellets from a shelf and then the vasculature of the forelimb region of the sensorimotor cortex contralateral to the reaching limb was removed. A control group received a posterior parietal cortex devasularization. Frame-by-frame video analysis of reaching behavior showed that the stages of the acquisition of skilled reaching and the stages of recovery after motor cortex stroke were similar. The animals sequentially learn three relationships or "oppositions" between a body part and the food target. The oppositions are invariant relationships but each can be achieved with movements that can vary from reach to reach and between rats. A snout-pellet opposition organizes the movements of orienting, a paw-pellet opposition organizes limb transport and grasping the pellet in the digits, and a mouth-pellet opposition organizes limb withdrawal and the release of the food into the mouth. The three oppositions and the movements that they recruit were disrupted after motor cortex damage, but not parietal cortex damage. The oppositions were reestablished after stroke in the order in which they were acquired prior to stroke. Enduring impairments were more noticeable in transport and withdrawal oppositions. That the stages of recovery from motor cortex stroke parallel those of initial acquisition are discussed in relation to contemporary explanations of diaschisis and the contribution of motor cortex to motor learning.

Attempt-dependent Decrease in Skilled Reaching Characterizes the Acute Postsurgical Period Following a Forelimb Motor Cortex Lesion: an Experimental Demonstration of Learned Nonuse in the Rat

Behavioural Brain Research. May, 2007  |  Pubmed ID: 17346809

The notion that shock or diaschisis is a distinctive stage in the recovery process following brain damage has played a formative role in the characterization of brain injury. For example, damage to the forelimb region of motor cortex results in an acute period of behavioural depression in skilled reaching and other skilled actions followed by improved performance mediated by compensatory movements. Whereas the progression of improvement and the use of compensatory movements in the chronic period of recovery is well-documented, temporal aspects of behaviour during the acute period of depression of behaviour are relatively unstudied. The present study examined the temporal scheduling of reach-attempts by rats attempting to gain single pellets of food from a shelf in a skilled reaching task. Pretrained rats received contralateral-to-the-pretrained limb forelimb motor cortex lesions. Control lesions included contralateral-to-the-pretrained limb parietal cortex lesions, or ipsilateral-to-the-pretrained limb motor cortex lesions. Frame-by-frame video analysis of behaviour showed a decrease in reaching attempts as a function of successive approaches and attempts to grasp the food over the first few postsurgical days in rats with contralateral-to-the-pretrained limb motor cortex lesions. A similar approach-dependent decrease in attempts did not occur after parietal or ipsilateral-to-the-pretrained limb motor cortex lesions. The decrease in responding occurred only during acute testing and was not observed in rats first tested after 8 days of postoperative recovery. The findings are discussed in relation to the ideas that: (1) the stroke subject is an active participant in modifying behaviour to cope with injury; (2) learned nonuse contributes to behaviour in the acute postinjury period following motor cortex injury; (3) diaschisis inadequately accounts for poststoke behaviour.

Similar Development of Cued and Learned Home Bases in Control and Hippocampal-damaged Rats in an Open Field Exploratory Task

Hippocampus. 2007  |  Pubmed ID: 17372977

Spatial behavior was examined in control rats and rats with neurotoxic-induced damage of the hippocampus in an open field "exploratory" task. In Experiment 1, rats were placed on a large circular table for 30 min for four consecutive days with a short wall adjacent to the table and a large black box near the edge of the table diametrically opposite to the wall. On the fifth day, rats were given a probe test during which both cues were removed. Over the training exposures both control and hippocampal-damaged rats formed "home bases," operationally defined as places where the rats preferentially stopped and spent time, near the cues. When the cues were removed on the probe day, both groups visited, stopped near, and spent time at places adjacent to the cues' previous location. In Experiment 2, rats were given a similar training protocol, but only a single cue was used, which was a small box placed directly on the table that did not block visibility of the entire room. On the fifth day, the box was moved to the other end of the table. Despite the presence of a cued home base, control and hippocampal-damaged rats remembered the original location of the home base. The results are discussed in relation to the comparative task demands of formal and informal test procedures and with respect to their relevance to understanding the neural basis of spatial behavior.

Parkinsonian Deficits in Context-dependent Regulation of Standing Postural Control

Neuroscience Letters. May, 2007  |  Pubmed ID: 17403570

This study explored whether patients with Parkinson's disease alter the regulation of upright standing according to constraints imposed by the environmental context. The provision of context-dependent adaptations was inferred from the presence of adjustments to standing postural control that would serve to reduce fall risk when balance was challenged by a threatening environmental context. Participants were asked to stand as still as possible in two environmental context conditions that differed in the level of imposed postural threat: LOW threat and HIGH threat. Eight levodopa dependent patients with Parkinson's disease (PD) and eight age-matched control subjects (CTRL) provided the subject sample. PD patients were tested following a 12-h withdrawal of anti-Parkinsonian medications and approximately 1h post-medication. The CTRL group showed altered postural control in the HIGH threat condition, in a manner that was indicative of appropriate context-dependent regulation of standing. PD patients, in the non-medicated or medicated states, did not modify stance regulation when the environmental context heightened postural threat. Our results extend the current understanding of Parkinsonian deficits in the context-dependent regulation of postural control to include upright standing.

No Improvement by Amphetamine on Learned Non-use, Attempts, Success or Movement in Skilled Reaching by the Rat After Motor Cortex Stroke

The European Journal of Neuroscience. Jun, 2007  |  Pubmed ID: 17553013

Amphetamine (AMPH) has been proposed as a treatment for post-stroke motor deficits when coupled with symptom-relevant physical rehabilitation. Whereas a number of experimental studies report improvements in endpoint measures of skilled reaching for food by rats, there has been no assessment of whether beneficial effects extend to overcoming learned non-use of the limb in the acute post-stroke period or to the qualitative deficits in movement in the chronic post-stroke period. In addition to evaluating the effects of AMPH on success, these were the objectives of the present study. In three different reaching experiments, groups of rats were pre-trained in skilled reaching for food prior to receiving a motor cortex stroke via pial removal. Postoperatively the rats received periodic AMPH treatment and daily rehabilitation. In the acute post-stroke period, AMPH failed to prevent the development of learned non-use of the limb, and in the acute and chronic period failed to improve recovery of reaching success, and also failed to improve the qualitative aspects of reaching movements. Nevertheless, AMPH did enhance adjunct non-reaching movements of locomotion, rearing and turning. The results are discussed in relation to the idea that the beneficial effects of post-stroke AMPH treatment do not extend to all movements, especially the movements of a forelimb in retrieving and consuming food.

The Point of Entry Contributes to the Organization of Exploratory Behavior of Rats on an Open Field: an Example of Spontaneous Episodic Memory

Behavioural Brain Research. Aug, 2007  |  Pubmed ID: 17590451

The exploratory behavior of rats on an open field is organized in that animals spend disproportionate amounts of time at certain locations, termed home bases, which serve as centers for excursions. Although home bases are preferentially formed near distinctive cues, including visual cues, animals also visit and pause and move slowly, or linger, at many other locations in a test environment. In order to further examine the organization of exploratory behavior, the present study examined the influence of the point of entry on animals placed on an open field table that was illuminated either by room light or infrared light (a wavelength in which they cannot see) and near which, or on which, distinctive cues were placed. The main findings were that in both room light and infrared light tests, rats visited and lingered at the point of entry significantly more often than comparative control locations. Although the rats also visited and lingered in the vicinity of salient visual cues, the point of entry still remained a focus of visits. Finally, the preference for the point of entry increased as a function of salience of the cues marking that location. That the point of entry influences the organization of exploratory behavior is discussed in relation to the idea that the exploratory behavior of the rat is directed toward optimizing security as well as forming a spatial representation of the environment.

A Golgi Analysis of Cortical Pyramidal Cells in the Unilateral Parkinson Rat: Absence of Change in the Affected Hemisphere Vs Hypertrophy in the Intact Hemisphere

Restorative Neurology and Neuroscience. 2007  |  Pubmed ID: 17726267

Unilateral dopamine (DA) depletion in the rat provides an analog of human Parkinson's disease. The classic view of DA loss is that it produces changes in the activity of striatal-cortical circuitry that results in reduced frontal cortex neural activity. This "functional deafferent" view is consistent with findings that animals display sensorimotor deficits in the contralateral-to-lesion side of the body and compensatory behavior adjustments in the ipsilateral-to-lesion side of the body. The present study examined how DA depletion and the associated sensorimotor changes affect the morphology of the ipsilateral or contralateral neocortex neurons as assessed by dendritic morphology in Golgi-stained tissue.

Recovery of Skilled Reaching Following Motor Cortex Stroke: Do Residual Corticofugal Fibers Mediate Compensatory Recovery?

The European Journal of Neuroscience. Dec, 2007  |  Pubmed ID: 18028116

Motor cortex (MC) injury impairs skilled reaching in rats, but success scores are eventually restored to approximate preoperative levels. The improvement is attributed to compensatory strategies, such as substituting trunk rotations for the chronically lost rotatory movement of the forelimb, that occur during transport and withdrawal. The present study examined the contributions of the rostral motor cortex (RMC) and the caudal motor cortex (CMC) to skilled reaching performance. The study also examined the role of the ipsilateral and the contralateral hemispheres in supporting the spontaneous recovery. Rats were trained to reach for single food pellets, and their recovery from partial or complete MC injury was documented with quantitative scores and movement element measures in three experiments: (1) devascularization of the CMC, or the RMC, or both, in the hemisphere contralateral to the reaching paw; (2) additional lesions to the CMC and RMC injuries such that the conjoint damage amounted to an MC lesion; and (3) MC lesion followed by damage in the neocortex lateral to the injury or in the opposite MC. The results showed that the CMC made the main contribution to skilled reaching performance, and that there was a lesser contribution by the RMC. MC damage was exacerbated by additional damage to the ipsilateral neocortex as compared to the contralateral neocortex. The results are discussed in relation to the idea that the involvement of the neocortical areas in skilled reaching performance and its recovery is proportional to the region from which corticospinal projections originate.

"Learned Baduse" Limits Recovery of Skilled Reaching for Food After Forelimb Motor Cortex Stroke in Rats: a New Analysis of the Effect of Gestures on Success

Behavioural Brain Research. Apr, 2008  |  Pubmed ID: 18155782

Trauma or stroke to motor cortex (MtCx) results in motor impairments that include movements of the contralateral forelimb in reaching for food that is to be placed in the mouth for eating (skilled reaching). In the rat, post-lesion recovery of success is incomplete and achieved using compensatory movements. A striking and puzzling feature of post-lesion performance is an increase in the numbers of reaching attempts. Whereas successful movements, whether normal or compensatory, have been extensively described, there has been no previous analysis of the movements comprising reach attempts, especially those that are unsuccessful. Here, rats pretrained in a single pellet reaching task received MtCx stroke via pial removal contralateral to the preferred-for-reaching forelimb. They then received daily physical rehabilitation and assessment in reaching. In addition to conventional end-point measures of performance, reaching behavior was evaluated by a new measure, gestures, derived from Laban Movement Analysis. Gestural analysis describes all non-weight bearing limb movements and so can document movements not explicitly directed to, or successful in, grasping food. In the acute post-stroke period, MtCx rats made few gestures, but thereafter gesture number escalated with recovery time, and eventually exceeded preoperative levels. Gestures were frequently repetitive and included combinations not used prior to stroke. The escalation in gestures number with recovery training suggests that excessive and inappropriate gestures may represent motor habits that substitute for, and compete with, successful movements. This description of "learned baduse" furthers the understanding of MtCx contributions to skilled movements and could potentially contribute to the modification of rehabilitative strategies for the treatment of stroke.

The Problem of Relating Plasticity and Skilled Reaching After Motor Cortex Stroke in the Rat

Behavioural Brain Research. Sep, 2008  |  Pubmed ID: 18282620

The plasticity of the nervous system is illustrated in the many new neuronal connections that are formed during the acquisition of behavioral skills, loss of function after brain injury, and subsequent recovery of function. The present review describes the acquisition of skilled reaching, the act of reaching for food with a forelimb, and the changes that take place in skilled reaching following motor cortex stroke. The review then discusses the difficulty in associating plastic changes with specific aspects of behavioral change. Skilled reaching behavior is complex and consists of a number of oppositions (stimulus response relationships), between the rat and the food target, a number of forelimb gestures (non-weight supporting movements), which are performed to obtain food, and a complex series of segmental movements (of the limb, head, and trunk), all of which influence the success of the act. Measures of these four aspects of skilled reaching behavior following motor cortex stroke reveal that there are a number of learned changes that take place at different times, including learned nonuse, learned bad-use, and forgetting. The widespread dendritic proliferation, axonal growth, and synaptic formation that take place both before and after stroke are difficult to precisely relate to these behavioral changes. Whereas plasticity is usually proposed to be associated with improved performance it is suggested that future work should attempt to better relate plastic changes to the details of behavioral changes.

Cineradiographic (video X-ray) Analysis of Skilled Reaching in a Single Pellet Reaching Task Provides Insight into Relative Contribution of Body, Head, Oral, and Forelimb Movement in Rats

Behavioural Brain Research. Oct, 2008  |  Pubmed ID: 18514337

The forelimb movements (skilled reaching) used by rats to reach for a single food pellet to place into the mouth have been used to model many neurological conditions. They have been described as a sequence of oppositions of head-pellet, paw-pellet and pellet-mouth that can be described as movements of the distal portion of body segments in relation to their fixed proximal joints. Movement scoring is difficult, however, because the location and movement of body segments is estimated through the overlying fur and skin, which is pliable and partially obscures movement. Using moderately high-speed cineradiographic filming from lateral, dorsal, and frontal perspectives, the present study describes how forelimb and skeletal bones move during the skilled reaching act. The analysis indicates that: (i) head movements for orienting to food, enabled by the vertical orientation of the rostral spinal cord, are mainly independent of trunk movement, (ii) skilled reaching consists of a sequence of upper arm and extremity movements each involving a number of concurrent limb segment and joint movements and (iii) food pellets are retrieved from the paw using either the incisors and/or tongue. The findings are discussed in relation to the idea that X-ray cinematography is valuable tool for assisting descriptive analysis and can contribute to understanding general principles of the relations between whole body, head, oral, and upper extremity movement.

Visual Guidance for Hand Advance but Not Hand Withdrawal in a Reach-to-eat Task in Adult Humans: Reaching is a Composite Movement

Journal of Motor Behavior. Jul, 2008  |  Pubmed ID: 18628110

Many animal species use reaching for food to place in the mouth (reach-to-eat) with a hand, and it may be a primitive movement. Although researchers (I. Q. Whishaw, 2005; A. N. Iwaniuk & I. Q. Whishaw, 2000; M. Gentiluci, I. Toni, S. Chieffi, & G. Pavesi, 1994) have described visual guidance of reaching in both normal and brain-injured human and nonhuman primates, researchers have not described the contribution of vision during advance of the limb to grasp food and during withdrawal of the limb with food to the mouth. To evaluate visual contributions, the authors monitored eye movements in young adults as they reached for food with and without vision. Participants visually engaged the target prior to the 1st hand movement and disengaged it as the food was grasped. Visual occlusion slowed limb advance and altered digit shaping but did not affect withdrawal. The dependence on visual control of advance but not withdrawal suggests that the reach-to-eat movement is a composite of 2 basic movements under visual and tactile/proprioceptive guidance, respectively.

Intact Intracortical Microstimulation (ICMS) Representations of Rostral and Caudal Forelimb Areas in Rats with Quinolinic Acid Lesions of the Medial or Lateral Caudate-putamen in an Animal Model of Huntington's Disease

Brain Research Bulletin. Sep, 2008  |  Pubmed ID: 18639744

Neurotoxic, cell-specific lesions of the rat caudate-putamen (CPu) have been proposed as a model of human Huntington's disease and as such impair performance on many motor tasks, including skilled forelimbs tasks such as reaching for food. Because the CPu and motor cortex share reciprocal connections, it has been proposed that the motor deficits are due in part to a secondary disruption of motor cortex. The purpose of the present study was to examine the functionality of the motor cortex using intracortical microstimulation (ICMS) following neurotoxic lesions of the CPu. ICMS maps have been shown to be sensitive indicators of motor skill, cortical injury, learning, and experience. Long-evans hooded rats received a sham, a medial, or a lateral CPu lesion using the neurotoxin, quinolinic acid (2,3-pyridinedicarboxylic acid). Two weeks later the motor cortex was stimulated under light ketamine anesthesia. Neither lateral nor medial lesions of the CPu altered the stimulation threshold for eliciting forelimb movements, the type of movements elicited, or the size of the rostral forelimb (RFA) and caudal forelimb areas (CFA) from which movements were elicited. The preservation of ICMS forelimb movement representations (the forelimb map) in rats with cell-specific CPu lesions suggests motor impairments following lesions of the lateral striatum are not due to the disruption of the motor map. Therefore, the impairments that follow striatal cell loss are due either to alterations in circuitry that is independent of motor cortex or to alterations in circuitry afferent to the motor cortex projections.

Bilateral Impairments of Skilled Reach-to-eat in Early Parkinson's Disease Patients Presenting with Unilateral or Asymmetrical Symptoms

Behavioural Brain Research. Dec, 2008  |  Pubmed ID: 18692094

Previous studies have described limb and hand movement abnormalities in a reach-to-eat task in advanced Parkinson's disease (PD) and animal models of PD. The present study was directed toward examining reach-to-eat movements in early PD patients untreated with medication, along with a follow-up examination of a PD patient sub-group who were treated with a symptomatically stable dosage of dopamine replacement. Analysis of the reach-to-eat movement was made using blinded assessment under a validated scoring system, and comparisons were made on the total reach score and reach sub-component scores. In both examinations, PD patients had unilateral deficits or significant deficit asymmetry, as indicated by Unified Parkinson's Disease Rating Scale (UPDRS) scores. UPDRS motor scores were higher for the most-affected side of the body (mean scores of 10.45 and 4.25 for more- and less-affected upper limbs, respectively), whereas reach scores were equivalently impaired for the two sides (median scores of 12.35 and 12.56 for more- and less-affected limbs, respectively). These differences between clinical and experimental assessments of motor impairments persisted among early PD patients treated with medication. Thus, functional reaching shows bilateral and symmetrical abnormalities in early PD patients, even when clinical assessment shows asymmetrical or even unilateral impairment. These findings suggest that functional qualitative reaching evaluation is a sensitive test in early PD, and that significant bilateral abnormalities in reach function are present even in pre-clinical stages of the disease.

Motor Cortex Stroke Impairs Individual Digit Movement in Skilled Reaching by the Rat

The European Journal of Neuroscience. Jul, 2008  |  Pubmed ID: 18702702

Over 30 years ago, Castro [(1972) Brain Res., 37, 173-185] proposed that motor cortex (MtCx) ablation produced deficits in digital usage that contributed to the rat's impairments in a reach-to-eat task, but the impairment was not directly documented. The present study examined digit use in control rats and rats with MtCx lesions using high-speed (1000 f/s) video recording. Temporal and spatial characteristics of individual digits were evaluated by digitizing the tip of the digits and digital joints using the motion measurement system Peak Motus. Control rats displayed differential digital use during grasping actions and MtCx damage reduced individual digit movement, both as the paw was pre-shaped for grasping and in the grasping action itself. The findings show that although grasping is retained following MtCx damage, MtCx is essential for dexterous movement. The results are discussed in relation to the idea that rodent MtCx is not only necessary for rotatory movements of the limb, but also for digital control and in relation to the similarities of rodent digit use to that described for primates.

Transient Middle Cerebral Artery Occlusion Disrupts the Forelimb Movement Representations of Rat Motor Cortex

The European Journal of Neuroscience. Sep, 2008  |  Pubmed ID: 18717732

Infarcts from proximal middle cerebral artery (MCA) stroke can produce impairments in motor function, particularly finger movements in humans and digit flexion in rats. In rats, the extent of neural damage may be limited to basal ganglia structures or may also include portions of the frontal and parietal cortex in severe cases. Although the primary motor cortex (M1) is anatomically spared in proximal MCA occlusion, its functional integrity is suspect because even a small subcortical infarct can damage neural circuits linking M1 with basal ganglia, brainstem, and spinal cord. This motivated the present study to investigate the neurophysiological integrity of M1 after transient proximal MCA occlusion. Rats, preoperatively trained and non-preoperatively trained to reach for food, received extensive reach training/testing with the contralateral-to-lesion paw for several weeks after MCA occlusion. The forelimb movement representations were assayed from the ipsilateral-to-lesion M1 with intracortical microstimulation approximately 10 weeks after MCA occlusion. Digit flexion was impaired during food grasping in rats with relatively small subcortical infarcts and was completely abolished in rats that sustained at least moderate subcortical damage. Corresponding forelimb movement representations ranged from abnormally small to absent. The results suggest that ischemia in subcortical territories of the MCA does not spare the neurophysiological properties of M1 despite its apparent anatomical intactness, probably because of damage sustained to its descending fibers. Thus, M1 dysfunction contributes to the impairments that ensue from proximal MCA occlusion, even when the infarct is limited to subcortical regions.

Hind Limb Stepping over Obstacles in the Horse Guided by Place-object Memory

Behavioural Brain Research. Mar, 2009  |  Pubmed ID: 19071161

An animal that has stepped over an obstacle with its forelimbs uses a memory of the obstacle to guide the hind limbs so that they also clear the obstacle, even in situations in which long pauses are introduced between forelimb and hind limb stepping. To further clarify the features of hind limb obstacle clearance memory, the present study examined hind limb obstacle clearance in the horse. A rider guided horses over obstacles and paused the horse over obstacles in tests that examined the relationship between forelimb and hind limb stepping, with the following results. First, the horses displayed memory for an obstacle as measured by hind limb lifting over the obstacle for durations lasting as long as 15 min. The response was not dependent upon ongoing visualization of the obstacle, as limb lifting was unaffected by visual occlusion with blinders, a blindfold, or by removing the obstacle during the pause. Second, previous experience of stepping over an obstacle led to pause-related hind limb lifting at the object's previous location even on trials for which there was no obstacle and so no preceding forelimb lifting. Third, whereas a horse would lift its hind limbs to clear two successively presented obstacles, replacing an obstacle before the horse after the forelimbs had cleared the obstacle prevented subsequent hind limb lifting at the obstacle's previous location. Taken together the results show that hind limb obstacle clearance is guided by a place-object memory. The results are discussed in relation to the differential sensory and memonic control of forelimb and hind limb stepping with the suggestion that place-object memory can guide hind stepping as well as overshadow working memory from front leg stepping.

Nicotine Does Not Improve Recovery from Learned Nonuse nor Enhance Constraint-induced Therapy After Motor Cortex Stroke in the Rat

Behavioural Brain Research. Mar, 2009  |  Pubmed ID: 19100291

Nicotine, a cholinergic agonist, rapidly crosses the blood-brain barrier, promotes neuronal plasticity and has been suggested to enhance behavior in a variety of neurological conditions. Nicotine has also been suggested to benefit functional recovery in rodent models of stroke. At present there has been no systematic investigation of the potential benefits of nicotine therapy in both the acute and chronic post-stroke period. This was the objective of the present study and to that end, the effects of nicotine administration prior to and following motor cortex stroke were examined in a skilled reaching task. The task provides a thorough assessment of learned nonuse and constraint-induced recovery of behavior as determined by both end-point and movement element analysis. Nicotine (0.3 mg/kg p.o.) was administered twice daily during reach training and following motor cortex stroke. Rats were divided into four groups based on their pre-/post-stroke treatment: nicotine/nicotine, nicotine/vehicle, vehicle/nicotine, vehicle/vehicle. After stroke, nicotine did not counteract learned nonuse, facilitate constraint-induced therapy, or improve long-term recovery as measured by end-point analysis and movement element analysis. The results are discussed in relation to the problem of identifying pharmacotherapeutic agents that augment rehabilitation following stroke.

Both Compensation and Recovery of Skilled Reaching Following Small Photothrombotic Stroke to Motor Cortex in the Rat

Experimental Neurology. Jul, 2009  |  Pubmed ID: 19409894

Large lesions produced by stroke to the forelimb region of motor cortex of the rat feature post-stroke improvement that in the main is due to compensation. The present study describes both recovery and compensation of forelimb use in a reach-to-eat (skilled reaching) task following small photothrombotic stroke. The rats were pretrained before stroke, and then assessed using endpoint measures and biometric movement analysis during rehabilitation in the acute and chronic post-stroke periods. Histological and MRI analysis indicated that the stroke consisted of a small lesion surrounded by cortex featuring scattered cell loss, likely of the large pyramidal cells that characterize the forelimb region of motor cortex. The stroke reduced reaching success, especially on the most demanding measure of success on first reach attempts, in the acute period, but with rehabilitation, performance returned to pre-stroke levels. Reach movements as assessed by biometric measures were severely impaired acutely but displayed significant recovery chronically although this recovery was not complete. The results suggest that not only do rats show post-stroke compensation in skilled reaching but they can also display functional recovery. It is suggested that recovery is mediated by the spared neurons in the peri-infarct region of forelimb motor cortex. The results demonstrate the utility of a small lesion model for studying post-stroke neural and behavioral change and support the view that optimal post-stroke treatment should be directed toward limiting tissue loss.

Similar Hand Shaping in Reaching-for-food (skilled Reaching) in Rats and Humans Provides Evidence of Homology in Release, Collection, and Manipulation Movements

Behavioural Brain Research. Dec, 2009  |  Pubmed ID: 19520119

Many animal species use their forelimbs to assist in eating, such as occurs in a reach-to-eat task (skilled reaching) in which a forelimb is extended to grasp food that is placed in the mouth for eating. It is unclear the extent to which the skilled reaching movements of different species share common ancestry and so are homologous or evolved independently and so are analogous (homoplasy). Here hand shaping (the movements of the hand and digits) that occur as the hand is transported to the target, were examined using high-speed (1000 frames/s) video recording and kinematic measurement (Peak Motus) in the rat (Rattus norvegicus) and human (Homo sapiens). Ten movement similarities were identified from the point that the limb initiated transport towards the food item to the point that the food was grasped. The digits were closed and semi-flexed as the hand was lifted (released from a substrate) and supinated. They closed further as the hand was collected for aiming. They then extended as the hand was transported to the target and then opened in conjunction with pronation to orient the hand for grasping (manipulation). Finally the digits were flexed and closed for grasping. These movements occurred at approximately the same point of limb transport in both species even though the rat used a whole paw grasp and the humans used a pincer grasp. Bushbabies (Galago garnettii), titi monkeys (Callicebus brunneus), rhesus monkeys (Macaca mulatta) and the bonobo (Pan paniscus) displayed similar hand shaping in skilled reaching despite species differences in grasping movements. Homologous hand shaping in the rodent clade and the primate clade and within the primate lineage is discussed in relation to its possible derivation from hand shaping movements associated with stepping.

Righting Elicited by Novel or Familiar Auditory or Vestibular Stimulation in the Haloperidol-treated Rat: Rat Posturography As a Model to Study Anticipatory Motor Control

Journal of Neuroscience Methods. Sep, 2009  |  Pubmed ID: 19559052

External cues, including familiar music, can release Parkinson's disease patients from catalepsy but the neural basis of the effect is not well understood. In the present study, posturography, the study of posture and its allied reflexes, was used to develop an animal model that could be used to investigate the underlying neural mechanisms of this sound-induced behavioral activation. In the rat, akinetic catalepsy induced by a dopamine D2 receptor antagonist (haloperidol 5mg/kg) can model human catalepsy. Using this model, two experiments examined whether novel versus familiar sound stimuli could interrupt haloperidol-induced catalepsy in the rat. Rats were placed on a variably inclined grid and novel or familiar auditory cues (single key jingle or multiple key jingles) were presented. The dependent variable was movement by the rats to regain equilibrium as assessed with a movement notation score. The sound cues enhanced movements used to regain postural stability and familiar sound stimuli were more effective than unfamiliar sound stimuli. The results are discussed in relation to the idea that nonlemniscal and lemniscal auditory pathways differentially contribute to behavioral activation versus tonotopic processing of sound.

Individual Differences in Skilled Reaching for Food Related to Increased Number of Gestures: Evidence for Goal and Habit Learning of Skilled Reaching

Behavioral Neuroscience. Aug, 2009  |  Pubmed ID: 19634947

Skilled reaching in rodents and primate is motorically similar, but success in reaching by rodents is distinctively variable. The source of this variability has not been examined previously. Long-Evans rats were videotaped as they reached for food in 2 different reaching tasks, and endpoint measures of performance were examined in relation to variables previously associated with individual differences, including testing procedures, rehabilitation, movement ability, general locomotor activity, and cortical anatomy. There were individual differences in performance, but these were not related to the dependent measures related to training, movement ability, locomotor activity, or anatomy (e.g., brain with cortical thickness, acetylcholinesterase and neuron density, pyramidal tract size). Success was negatively related to numbers of gestures (non-weight-bearing movements of the reaching limb) used on a reach, however. The results are discussed in relation to the idea that individual differences in response strategy bias some rats to use a more successful goal strategy and others to use a less successful habit strategy for skilled reaching.

Music Attenuates Excessive Visual Guidance of Skilled Reaching in Advanced but Not Mild Parkinson's Disease

PloS One. 2009  |  Pubmed ID: 19718260

Parkinson's disease (PD) results in movement and sensory impairments that can be reduced by familiar music. At present, it is unclear whether the beneficial effects of music are limited to lessening the bradykinesia of whole body movement or whether beneficial effects also extend to skilled movements of PD subjects. This question was addressed in the present study in which control and PD subjects were given a skilled reaching task that was performed with and without accompanying preferred musical pieces. Eye movements and limb use were monitored with biomechanical measures and limb movements were additionally assessed using a previously described movement element scoring system. Preferred musical pieces did not lessen limb and hand movement impairments as assessed with either the biomechanical measures or movement element scoring. Nevertheless, the PD patients with more severe motor symptoms as assessed by Hoehn and Yahr (HY) scores displayed enhanced visual engagement of the target and this impairment was reduced during trials performed in association with accompanying preferred musical pieces. The results are discussed in relation to the idea that preferred musical pieces, although not generally beneficial in lessening skilled reaching impairments, may normalize the balance between visual and proprioceptive guidance of skilled reaching.

Hippocampal Damage Produces Retrograde but Not Anterograde Amnesia for a Cued Location in a Spontaneous Exploratory Task in Rats

Hippocampus. Sep, 2010  |  Pubmed ID: 19957337

Performance in several memory tasks is known to be unaffected by hippocampal damage sustained before learning, but is severely disrupted if the same damage occurs after learning. Memories for preferred locations, or home bases, in exploratory tasks can be formed by rats with hippocampal damage, but it is unknown if the memory for a home base survives hippocampal damage. To examine this question, for 30 min each day for five consecutive days, rats explored a circular open field containing one local cue. By Day 5 the rats preferentially went directly to that location, spent the majority of their time at that location, made rapid direct trips to that location when returning from an excursion and so demonstrated that the location was a home base. Memory for the cued location was examined after a 24 h or 14-day interval with the cue removed. In Experiments 1 and 2, control rats and rats with prior N-methyl-D-aspartic acid hippocampal lesions demonstrated memory of the home base location by making direct trips to that location. In Experiment 3, rats that had first explored the open field and cue and then received hippocampal lesions showed no memory for the cued location. The absence of anterograde impairment vs. the presence of retrograde impairment for memory of a spatial home base confirms a role for the hippocampus in the retention of spatial memory acquired during exploration.

Development of Collection Precedes Targeted Reaching: Resting Shapes of the Hands and Digits in 1-6-month-old Human Infants

Behavioural Brain Research. Dec, 2010  |  Pubmed ID: 20451560

Hand shaping is an important part of many skilled hand movements and includes a number of hand shapes prominent amongst which is collection. In collection, the hand is held with the digits lightly closed and flexed. It occurs when the hand is at rest and it occurs as the hand is transported to a target in behaviors such as reaching for an object, crawling, and climbing a ladder. Collection also frequently precedes hand gestures associated with speaking. The development of collection in infancy has not been described but it might be predicted that collection should develop before grasping and reaching movements. The present study examines the development of collection and arm position during the first 6 months of infant development. Infants were filmed while awake and photographed while asleep and hand shape and the hands location relative to the torso was documented. Collection associated with a relaxed position of the arm became increasingly prominent over the first 4 weeks of life in both awake and sleeping infants. It replaces a clenched (spastic) fist that was typically held proximal to the upper torso. The results are discussed in relation to the idea that the development of collection is an important antecedent to other hand shaping movements, especially skilled movements of grasping and reaching.

Challenging Context Affects Standing Reach Kinematics Among Parkinson's Disease Patients

Behavioural Brain Research. Dec, 2010  |  Pubmed ID: 20478337

The standing reach movement requires coordinated activation of postural and focal motor responses. For PD patients, both components of this reaching task exhibit evidence of motor deficit. In the present experiment, we examined these motor responses during a standing reaching task in a challenging environmental context. PD patients (n=10) and control participants (n=8) were asked to reach and drink from a glass while standing on a raised platform (0.6m) with and without an additional anterior platform. Removal of the anterior platform placed participants in a higher postural threat context. Displacement data were captured from markers on relevant body landmarks to provide reach end-point and whole-body movement kinematics. Our results showed that PD patients delayed trunk flexion and peak end-point velocity during the forward reach phase and peak centre of mass velocity during the transport phase for a challenged standing reach. These behaviours, in combination with the bradykinetic motor control observed in PD patients, could contribute to the frequent falls observed among the PD population.

The Functional Origins of Speech-related Hand Gestures

Behavioural Brain Research. Dec, 2010  |  Pubmed ID: 20573589

Many theories of language posit its recent evolution, perhaps contemporaneous with the evolution of Homo sapiens. The embodied language theory, however, in proposing that language includes gestures, provides an avenue for tracing language origins to phylogenetically earlier ancestral species. Here, evidence is presented that the structure of functional hand movements (e.g., reaching for food, climbing a ladder, or crawling), in rats and humans is similar. The structure of these functional hand movements is then compared to speech-related hand gestures in humans. The sequence of language-related gestures are also found to be characteristic of functional hand movements. It is suggested that these findings show that the arm and hand gestures that accompany human speech are derived from the same neural substrates that produce functional movements. Additionally, evidence is reviewed that supports the idea that speech-related gestures resemble the movements elicited by long-train stimulation of the primate motor cortex. Together, this evidence suggests that speech-related hand gestures have their evolutionary origins in functional hand movements of ancestral non-primate and primate species and may be constrained by the neural substrate for those movements. These findings are further discussed in relation to the idea that speech-related gestures reflect forelimb motor cortex contributions to embodied language.

Reaching-to-eat in Humans Post-stroke: Fluctuating Components Within a Constant Pattern

Behavioral Neuroscience. Dec, 2010  |  Pubmed ID: 21133536

Reaching movements of the arm and hand become automatic early in development and are used throughout one's life span. Studies on skilled reaching have focused on the kinematic aspects and have advanced our knowledge of the individual motor components of reaching. It has also been shown that motor behaviors are organized in terms of ethologically relevant actions, rather than by motor components. Thus, it is important to analyze how the motor components of reaching are performed within the overall action as a whole. The objective of the present study was to examine the motor components of reaching-to-eat within the context of the overall behavior in stroke participants. Results show that reaching-to-eat involves the whole body to produce isolated actions of the limb and changes after stroke in three fundamental ways: abnormal use of nonkinematic aspects of movement, body-limb disintegration, and a disruption in the temporal aspect of the phases of reaching-to-eat. The movements within the behavior can reorganize, possibly a reflection of dynamic interactions between behavioral compensation and neuroplasticity, while the overall performance of the behavior remains the same. Such subtle flexibility may be part of the process of recovery.

Hand Shaping in the Rat: Conserved Release and Collection Vs. Flexible Manipulation in Overground Walking, Ladder Rung Walking, Cylinder Exploration, and Skilled Reaching

Behavioural Brain Research. Jan, 2010  |  Pubmed ID: 19716849

Hand shaping in terrestrial mammals is adapted to many functions including walking, climbing, exploration, and skilled manipulation. Nevertheless, hand shaping is not well described in the rat (Rattus norvegicus) although the species is used to study the evolution of movement, the neural control of movement, and to model impairments that can result from brain injury. In the present study, rat hand movements were examined in standardized tests of overground walking, horizontal or inclined ladder rung walking, exploring a vertical wall of a cylinder, and skilled reaching for food. Behavior was filmed with high-speed (250-1000 f/s) video camera from which frame-by-frame behavioral and kinematic analyses (Peak Motus) were made. There were three hand actions common to all tasks. In release, the hand pushed off or was lifted from a substrate; in collection, the digits were closed and flexed though the midpoint of limb transport; and, in manipulation, the hand and digits were shaped to contact or grasp a target. The movements of release and collection, although variable in character, speed and duration, were very similar in the different tests. The movement of manipulation featured greater specialized digit use and varied sensory control (olfaction, vibrissae, and tactile senses) in different tasks. Conserved release and collection vs. the variability of manipulation is discussed in relation to the evolution, neural control, and neural commitment underlying hand movements.

Impaired Arpeggio Movement in Skilled Reaching by Rubrospinal Tract Lesions in the Rat: a Behavioral/anatomical Fractionation

Journal of Neurotrauma. Dec, 2011  |  Pubmed ID: 21612320

Spinal cord injury damaging the rubrospinal tract (RST) interferes with skilled forelimb movement, but identification of the precise role of the RST in this behavior is impeded by the difficulty of surgically isolating the RST from other pathways running within the lateral funiculus (LF). The present study used a skilled reaching task and a behavioral/anatomical dissection method to identify the contribution of the RST to skilled forelimb movement. Rats were trained on the skilled reaching task and subjected to lesions of the LF. Based on histological evaluation, the animals were assigned to large, medium, or small LF lesion size groups. End point and arm/hand/digit movements were subsequently identified for each group. Success was impaired in all groups, but the impairment was not related to lesion size. Frame-by-frame qualitative analysis of the video recordings revealed that large LF lesions abolished the elements of digits close, digits open, arpeggio, grasp, supination 2, and release. Medium LF lesions interfered with a subset of the movement elements that were shown to be affected by the large LF lesions, namely arpeggio and grasp. Only the arpeggio movement was compromised after small LF lesions. The results show that not only does the LF contribute to skilled reaching, but because the RST was likely to have been damaged in all lesion groups, the RST is more involved in hand rotation than in digit use. The results are discussed in relation to the fiber tracts that are likely to be damaged in the different LF lesion groups.

Subsystems of Sensory Attention for Skilled Reaching: Vision for Transport and Pre-shaping and Somatosensation for Grasping, Withdrawal and Release

Behavioural Brain Research. Jul, 2011  |  Pubmed ID: 21807029

Skilled reaching is a forelimb movement in which a subject reaches for a piece of food that is placed in the mouth for eating. It is a natural movement used by many animal species and is a routine, daily activity for humans. Its prominent features include transport of the hand to a target, shaping the digits in preparation for grasping, grasping, and withdrawal of the hand to place the food in the mouth. Studies on normal human adults show that skilled reaching is mediated by at least two sensory attention processes. Hand transport to the target and hand shaping are temporally coupled with visual fixation on the target. Grasping, withdrawal, and placing the food into the mouth are associated with visual disengagement and somatosensory guidance. Studies on nonhuman animal species illustrate that shared visual and somatosensory attention likely evolved in the primate lineage. Studies on developing infants illustrate that shared attention requires both experience and maturation. Studies on subjects with Parkinson's disease and Huntington's disease illustrate that decomposition of shared attention also features compensatory visual guidance. The evolutionary, developmental, and neural control of skilled reaching suggests that associative learning processes are importantly related to normal adult attention sharing and so can be used in remediation. The economical use of sensory attention in the different phases of skilled reaching ensures efficiency in eating, reduces sensory interference between sensory reference frames, and provides efficient neural control of the advance and withdrawal components of skilled reaching movements.

The Use of Rodent Skilled Reaching As a Translational Model for Investigating Brain Damage and Disease

Neuroscience and Biobehavioral Reviews. Dec, 2011  |  Pubmed ID: 22227413

Neurological diseases, including Parkinson's disease, Huntington's disease, and brain damage caused by stroke, cause severe motor impairments. Deficits in hand use are one of the most debilitating motor symptoms and include impairments in body posture, forelimb movements, and finger shaping for manipulating objects. Hand movements can be formally studied using reaching tasks, including the skilled reaching task, or reach-to-eat task. For skilled reaching, a subject reaches for a small food item, grasps it with the fingers, and places it in the mouth for eating. The human movement and its associated deficits can be modeled by experimental lesions to the same systems in rodents which in turn provide an avenue for investigating treatments of human impairments. Skilled reaching movements are scored using three methods: (1) end point measures of attempts and success, (2) biometric measures, and (3) movement element rating scales derived from formal descriptions of movement. The striking similarities between human and rodent reaching movements allow the analysis of the reach-to-eat movement to serve as a powerful tool to generalize preclinical research to clinical conditions.

Proximal Movements Compensate for Distal Forelimb Movement Impairments in a Reach-to-eat Task in Huntington's Disease: New Insights into Motor Impairments in a Real-world Skill

Neurobiology of Disease. Feb, 2011  |  Pubmed ID: 21059390

Huntington's disease (HD) causes severe motor impairments that are characterized by chorea, dystonia, and impaired fine motor control. The motor deficits include deficits in the control of the forelimb, but as yet there has been no comprehensive assessment of the impairments in arm, hand and digit movements as they are used in every-day tasks. The present study investigated the reaching of twelve HD subjects and twelve age-matched control subjects on a reach-to-eat task. The subjects were asked to reach for a small food item, with the left or the right hand, and then bring it to the mouth for eating. The task assesses the major features of skilled forelimb use, including orienting to a target, transport of the hand to a target, use of a precision grasp of the target, limb withdrawal to the mouth, and release of the food item into the mouth, and the integration of the movements into a smooth act. The movements were analyzed frame-by-frame by scoring the video record using an established movement element rating scale and by biometric analysis to describe limb trajectory. All HD subjects displayed greater reliance on more proximal movements in reaching. They also displayed overall jerkiness, a significant impairment in end point error correction (i.e. no smooth trajectories), deficits in timing and terminating motion (overshooting the target), impairments in rotation of the hand, abnormalities in grasping, and impairments in releasing the food item to the mouth. Although impairment in the control of the distal segments of the limb was common to all subjects, the intrusion of choreatic movements produced a pattern of highly variable performance between subjects. The quantification of reaching performance as measured by this analysis provides new insights into the impairments of HD subjects, allows an easily administered and inexpensive way to document the many skilled limb movement abnormalities, and relates the impairments to a real-world context. The protocol can serve as a useful clinical tool to evaluate innovative therapeutic interventions in HD such as physiotherapy, drug therapy, or functional neurosurgical procedures.

Drug Treatment and Familiar Music Aids an Attention Shift from Vision to Somatosensation in Parkinson's Disease on the Reach-to-eat Task

Behavioural Brain Research. Mar, 2011  |  Pubmed ID: 21073905

Sensory control of the natural skilled movement of reaching for a food target to eat (reach-to-eat) is closely coupled to the successive phases of the movement. Control subjects visually fixate the target from hand movement onset to the point that the digits contact the food, at which point they look away. This relationship between sensory attention and limb movement suggests that whereas limb advance is under visual control, grasping, limb withdrawal, and releasing the food to the mouth is guided by somatosensation. The pattern of sensory control is altered in Parkinson's disease (PD). PD subjects may visually fixate the target for longer durations prior to movement initiation, during the grasp, and during the initial portion of hand withdrawal suggesting that vision compensates for a somatosensory impairment. Because both medication and listening to favorite musical pieces have been reported to normalize some movements in subjects with PD, the present study compared the effect of medication and listening to preferred musical pieces on sensory attention shifts from vision to somatosensation during the reach-to-eat movement. Biometric measures of eye movement and the movement of the reaching limb were collected from PD subjects and aged-matched control subjects in four conditions in their own homes: off medication, off medication with music, on medication, and on medication with music. Unmedicated PD subjects were slower to visually disengage the target after grasping it. Their disengage latency was shortened by both music and medication. Medication and music did not improve other aspects of reaching, including reaching duration and the ratings of the movement elements of limb advance, grasping, and limb withdrawal. The results are discussed in relation to the idea that one way in which medication and music may aid movement in PD by normalizing somatosensory control of forelimb movement thus reducing compensatory visual monitoring.

The Consummatory Origins of Visually Guided Reaching in Human Infants: A Dynamic Integration of Whole-body and Upper-limb Movements

Behavioural Brain Research. Feb, 2012  |  Pubmed ID: 22326374

Reaching-to-eat (skilled reaching) is a natural behaviour that involves reaching for, grasping and withdrawing a target to be placed into the mouth for eating. It is an action performed daily by adults and is among the first complex behaviours to develop in infants. During development, visually guided reaching becomes increasingly refined to the point that grasping of small objects with precision grips of the digits occurs at about one year of age. Integration of the hand, upper-limbs, and whole body are required for successful reaching, but the ontogeny of this integration has not been described. The present longitudinal study used Laban Movement Analysis, a behavioural descriptive method, to investigate the developmental progression of the use and integration of axial, proximal, and distal movements performed during visually guided reaching. Four infants (from 7 to 40 weeks age) were presented with graspable objects (toys or food items). The first prereaching stage was associated with activation of mouth, limb, and hand movements to a visually presented target. Next, reaching attempts consisted of first, the advancement of the head with an opening mouth and then with the head, trunk and opening mouth. Eventually, the axial movements gave way to the refined action of one upper-limb supported by axial adjustments. These findings are discussed in relation to the biological objective of reaching, the evolutionary origins of reaching, and the decomposition of reaching after neurological injury.

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