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Find video protocols related to scientific articles indexed in Pubmed.
The metabotropic glutamate receptor, mGlu5, is required for extinction learning that occurs in the absence of a context change.
Hippocampus
PUBLISHED: 08-27-2014
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The metabotropic glutamate (mGlu) receptors and, in particular, mGlu5 are crucially involved in multiple forms of synaptic plasticity that are believed to underlie explicit memory. MGlu5 is also required for information transfer through neuronal oscillations and for spatial memory. Furthermore, mGlu5 is involved in extinction of implicit forms of learning. This places this receptor in a unique position with regard to information encoding. Here, we explored the role of this receptor in context-dependent extinction learning under constant, or changed, contextual conditions. Animals were trained over 3 days to take a left turn under 25% reward probability in a T-maze with a distinct floor pattern (Context A). On Day 4, they experienced either a floor pattern change (Context B) or the same floor pattern (Context A) in the absence of reward. After acquisition of the task, the animals were returned to the maze once more on Day 5 (Context A, no reward). Treatment with the mGlu5 antagonist, 2-methyl-6-(phenylethynyl) pyridine, before maze exposure on Day 4 completely inhibited extinction learning in the AAA paradigm but had no effect in the ABA paradigm. A subsequent return to the original context (A, on Day 5) revealed successful extinction in the AAA paradigm, but impairment of extinction in the ABA paradigm. These data support that although extinction learning in a new context is unaffected by mGlu5 antagonism, extinction of the consolidated context is impaired. This suggests that mGlu5 is intrinsically involved in enabling learning that once-relevant information is no longer valid. © 2014 The Authors. Hippocampus Published by Wiley Periodicals, Inc.
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Neurons in the pigeon nidopallium caudolaterale signal the selection and execution of perceptual decisions.
Eur. J. Neurosci.
PUBLISHED: 08-21-2014
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Sensory systems provide organisms with information on the current status of the environment, thus enabling adaptive behavior. The neural mechanisms by which sensory information is exploited for action selection are typically studied with mammalian subjects performing perceptual decision-making tasks, and most of what is known about these mechanisms at the single-neuron level is derived from cortical recordings in behaving monkeys. To explore the generality of neural mechanisms underlying perceptual decision making across species, we recorded single-neuron activity in the pigeon nidopallium caudolaterale (NCL), a non-laminated associative forebrain structure thought to be functionally equivalent to mammalian prefrontal cortex, while subjects performed a visual categorisation task. We found that, whereas the majority of NCL neurons unspecifically upregulated or downregulated activity during stimulus presentation, ~20% of neurons exhibited differential activity for the sample stimuli and predicted upcoming choices. Moreover, neural activity in these neurons was ramping up during stimulus presentation and remained elevated until a choice was initiated, a response pattern similar to that found in monkey prefrontal and parietal cortices in saccadic choice tasks. In addition, many NCL neurons coded for movement direction during choice execution and differentiated between choice outcomes (reward and punishment). Taken together, our results implicate the NCL in the selection and execution of operant responses, an interpretation resonating well with the results of previous lesion studies. The resemblance of the response patterns of NCL neurons to those observed in mammalian cortex suggests that, despite differing neural architectures, mechanisms for perceptual decision making are similar across classes of vertebrates.
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Recording single neurons' action potentials from freely moving pigeons across three stages of learning.
J Vis Exp
PUBLISHED: 06-26-2014
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While the subject of learning has attracted immense interest from both behavioral and neural scientists, only relatively few investigators have observed single-neuron activity while animals are acquiring an operantly conditioned response, or when that response is extinguished. But even in these cases, observation periods usually encompass only a single stage of learning, i.e. acquisition or extinction, but not both (exceptions include protocols employing reversal learning; see Bingman et al.(1) for an example). However, acquisition and extinction entail different learning mechanisms and are therefore expected to be accompanied by different types and/or loci of neural plasticity. Accordingly, we developed a behavioral paradigm which institutes three stages of learning in a single behavioral session and which is well suited for the simultaneous recording of single neurons' action potentials. Animals are trained on a single-interval forced choice task which requires mapping each of two possible choice responses to the presentation of different novel visual stimuli (acquisition). After having reached a predefined performance criterion, one of the two choice responses is no longer reinforced (extinction). Following a certain decrement in performance level, correct responses are reinforced again (reacquisition). By using a new set of stimuli in every session, animals can undergo the acquisition-extinction-reacquisition process repeatedly. Because all three stages of learning occur in a single behavioral session, the paradigm is ideal for the simultaneous observation of the spiking output of multiple single neurons. We use pigeons as model systems, but the task can easily be adapted to any other species capable of conditioned discrimination learning.
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Serotonin release in the caudal nidopallium of adult laying hens genetically selected for high and low feather pecking behavior: an in vivo microdialysis study.
Behav. Brain Res.
PUBLISHED: 03-26-2014
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Severe feather pecking (FP) is a detrimental behavior causing welfare problems in laying hens. Divergent genetic selection for FP in White Leghorns resulted in strong differences in FP incidences between lines. More recently, it was shown that the high FP (HFP) birds have increased locomotor activity as compared to hens of the low FP (LFP) line, but whether these lines differ in central serotonin (5-hydroxytryptamine, 5-HT) release is unknown. We compared baseline release levels of central 5-HT, and the metabolite 5-HIAA in the limbic and prefrontal subcomponents of the caudal nidopallium by in vivo microdialysis in adult HFP and LFP laying hens from the ninth generation of selection. A single subcutaneous d-fenfluramine injection (0.5 mg/kg) was given to release neuronal serotonin in order to investigate presynaptic storage capacity. The present study shows that HFP hens had higher baseline levels of 5-HT in the caudal nidopallium as compared to LFP laying hens. Remarkably, no differences in plasma tryptophan levels (precursor of 5-HT) between the lines were observed. d-fenfluramine increased 5-HT levels in both lines similarly indirectly suggesting that presynaptic storage capacity was the same. The present study shows that HFP hens release more 5-HT under baseline conditions in the caudal nidopallium as compared to the LFP birds. This suggests that HFP hens are characterized by a higher tonic 5-HT release.
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Evidence for interhemispheric conflict during meta-control in pigeons.
Behav. Brain Res.
PUBLISHED: 03-14-2014
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In birds each hemisphere receives visual input from the contralateral eye. Since birds have no corpus callosum, avian brains are often seen as 'natural split brains'. How do birds cope with situations, when both hemispheres are brought into conflict? If under such conditions one hemisphere completely determines the response, this is called meta-control. This phenomenon has recently been demonstrated in pigeons. The aim of the current study is to test, if meta-control results from an interhemispheric conflict that would require interhemispheric interaction, possibly via the commissura anterior. To this end, we trained pigeons in a forced-choice color discrimination task under monocular condition such that each hemisphere was trained with a different pair of colors. Subsequently, pigeons were binocularly tested with conflicting and non-conflicting stimulus patterns. Conflicting stimuli indeed produced a delayed reaction time as expected when two divergent decisions create a conflict. In addition, we sometimes observed a pecking pattern that seemed to represent the average of two discrepant and hemisphere-specific movements. Thus, pigeons possibly undergo interhemispheric conflict during meta-control even without a corpus callosum. However, also when having decided to peck a certain color, the planned movement trajectory of the other hemisphere sometimes compromises the final pecking movement.
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NSF workshop report: discovering general principles of nervous system organization by comparing brain maps across species.
Brain Behav. Evol.
PUBLISHED: 02-28-2014
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Efforts to understand nervous system structure and function have received new impetus from the federal Brain Research through Advancing Innovative Neurotechnologies (BRAIN) Initiative. Comparative analyses can contribute to this effort by leading to the discovery of general principles of neural circuit design, information processing, and gene-structure-function relationships that are not apparent from studies on single species. We here propose to extend the comparative approach to nervous system 'maps' comprising molecular, anatomical, and physiological data. This research will identify which neural features are likely to generalize across species, and which are unlikely to be broadly conserved. It will also suggest causal relationships between genes, development, adult anatomy, physiology, and, ultimately, behavior. These causal hypotheses can then be tested experimentally. Finally, insights from comparative research can inspire and guide technological development. To promote this research agenda, we recommend that teams of investigators coalesce around specific research questions and select a set of 'reference species' to anchor their comparative analyses. These reference species should be chosen not just for practical advantages, but also with regard for their phylogenetic position, behavioral repertoire, well-annotated genome, or other strategic reasons. We envision that the nervous systems of these reference species will be mapped in more detail than those of other species. The collected data may range from the molecular to the behavioral, depending on the research question. To integrate across levels of analysis and across species, standards for data collection, annotation, archiving, and distribution must be developed and respected. To that end, it will help to form networks or consortia of researchers and centers for science, technology, and education that focus on organized data collection, distribution, and training. These activities could be supported, at least in part, through existing mechanisms at NSF, NIH, and other agencies. It will also be important to develop new integrated software and database systems for cross-species data analyses. Multidisciplinary efforts to develop such analytical tools should be supported financially. Finally, training opportunities should be created to stimulate multidisciplinary, integrative research into brain structure, function, and evolution.
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NSF workshop report: discovering general principles of nervous system organization by comparing brain maps across species.
J. Comp. Neurol.
PUBLISHED: 02-14-2014
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Efforts to understand nervous system structure and function have received new impetus from the federal Brain Research through Advancing Innovative Neurotechnologies (BRAIN) Initiative. Comparative analyses can contribute to this effort by leading to the discovery of general principles of neural circuit design, information processing, and gene-structure-function relationships that are not apparent from studies on single species. We here propose to extend the comparative approach to nervous system 'maps' comprising molecular, anatomical, and physiological data. This research will identify which neural features are likely to generalize across species, and which are unlikely to be broadly conserved. It will also suggest causal relationships between genes, development, adult anatomy, physiology, and, ultimately, behavior. These causal hypotheses can then be tested experimentally. Finally, insights from comparative research can inspire and guide technological development. To promote this research agenda, we recommend that teams of investigators coalesce around specific research questions and select a set of 'reference species' to anchor their comparative analyses. These reference species should be chosen not just for practical advantages, but also with regard for their phylogenetic position, behavioral repertoire, well-annotated genome, or other strategic reasons. We envision that the nervous systems of these reference species will be mapped in more detail than those of other species. The collected data may range from the molecular to the behavioral, depending on the research question. To integrate across levels of analysis and across species, standards for data collection, annotation, archiving, and distribution must be developed and respected. To that end, it will help to form networks or consortia of researchers and centers for science, technology, and education that focus on organized data collection, distribution, and training. These activities could be supported, at least in part, through existing mechanisms at NSF, NIH, and other agencies. It will also be important to develop new integrated software and database systems for cross-species data analyses. Multidisciplinary efforts to develop such analytical tools should be supported financially. Finally, training opportunities should be created to stimulate multidisciplinary, integrative research into brain structure, function, and evolution.
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Transient inactivation of the pigeon hippocampus or the nidopallium caudolaterale during extinction learning impairs extinction retrieval in an appetitive conditioning paradigm.
Behav. Brain Res.
PUBLISHED: 02-14-2014
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The majority of experiments exploring context-dependent extinction learning employ Pavlovian fear conditioning in rodents. Since mechanisms of appetitive and aversive learning are known to differ at the neuronal level, we sought to investigate extinction learning in an appetitive setting. Working with pigeons, we established a within-subject ABA renewal paradigm based on Rescorla (Q J Exp Psychol 61:1793) and combined it with pharmacological interventions during extinction. From the fear conditioning literature, it is known that both prefrontal cortex and the hippocampus are core structures for context-specific extinction learning. Accordingly, we transiently inactivated the nidopallium caudolaterale (NCL, a functional analogue of mammalian prefrontal cortex) and the hippocampus in separate experiments by intracranial infusion of the sodium-channel blocker tetrodotoxin immediately before extinction training. We find that TTX in both structures non-specifically suppresses conditioned responding, as revealed by a reduction of response rate to both the extinguished conditioned stimulus and a control stimulus which remained reinforced throughout the experiment. Furthermore, TTX during extinction training impaired later extinction retrieval assessed under drug-free conditions. This was true when responding to the extinguished stimulus was assessed in the context of extinction but not when tested in the context of acquisition, although both contexts were matched with respect to their history of conditioning. These results indicate that both NCL and hippocampus are involved in extinction learning under appetitive conditions or, more specifically, in the consolidation of extinction memory, and that their contribution to extinction is context-specific.
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An oxytocin-induced facilitation of neural and emotional responses to social touch correlates inversely with autism traits.
Neuropsychopharmacology
PUBLISHED: 01-20-2014
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Social communication through touch and mutual grooming can convey highly salient socio-emotional signals and has been shown to involve the neuropeptide oxytocin (OXT) in several species. Less is known about the modulatory influence of OXT on the neural and emotional responses to human interpersonal touch. The present randomized placebo (PLC)-controlled within-subject pharmaco-functional magnetic resonance imaging (fMRI) study was designed to test the hypothesis that a single intranasal dose of synthetic OXT (24?IU) would facilitate both neural and emotional responses to interpersonal touch in a context- (female vs male touch) and trait- (autistic trait load) specific manner. Specifically, the experimental rationale was to manipulate the reward value of interpersonal touch independent of the intensity and type of actual cutaneous stimulation administered. Thus, 40 heterosexual males believed that they were touched by either a man or a woman, although in fact an identical pattern of touch was always given by the same female experimenter blind to condition type. Our results show that OXT increased the perceived pleasantness of female, but not male touch, and associated neural responses in insula, precuneus, orbitofrontal, and pregenual anterior cingulate cortex. Moreover, the behavioral and neural effects of OXT were negatively correlated with autistic-like traits. Taken together, this is the first study to show that the perceived hedonic value of human heterosexual interpersonal touch is facilitated by OXT in men, but that its behavioral and neural effects in this context are blunted in individuals with autistic traits.
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The ontogenesis of language lateralization and its relation to handedness.
Neurosci Biobehav Rev
PUBLISHED: 01-18-2014
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Dominance of the left hemisphere for many aspects of speech production and perception is one of the best known examples of functional hemispheric asymmetries in the human brain. Classic theories about its ontogenesis assume that it is determined by the same ontogenetic factors as handedness because the two traits are correlated to some extent. However, the strength of this correlation depends on the measures used to assess the two traits, and the neurophysiological basis of language lateralization is different from that of handedness. Therefore, we argue that although the two traits show partial pleiotropy, there is also a substantial amount of independent ontogenetic influences for each of them. This view is supported by several recent genetic and neuroscientific studies that are reviewed in the present article.
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Distribution of neurotransmitter receptors and zinc in the pigeon (Columba livia) hippocampal formation: A basis for further comparison with the mammalian hippocampus.
J. Comp. Neurol.
PUBLISHED: 01-17-2014
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The avian hippocampal formation (HF) and mammalian hippocampus share a similar functional role in spatial cognition, but the underlying neuronal mechanisms allowing the functional similarity are incompletely understood. To understand better the organization of the avian HF and its transmitter receptors, we analyzed binding site densities for glutamatergic AMPA, NMDA, and kainate receptors; GABAA receptors; muscarinic M1 , M2 and nicotinic (nACh) acetylcholine receptors; noradrenergic ?1 and ?2 receptors; serotonergic 5-HT1A receptors; dopaminergic D1/5 receptors by using quantitative in vitro receptor autoradiography. Additionally, we performed a modified Timm staining procedure to label zinc. The regionally different receptor densities mapped well onto seven HF subdivisions previously described. Several differences in receptor expression highlighted distinct HF subdivisions. Notable examples include 1) high GABAA and ?1 receptor expression, which rendered distinctive ventral subdivisions; 2) high ?2 receptor expression, which rendered distinctive a dorsomedial subdivision; 3) distinct kainate, ?2 , and muscarinic receptor densities that rendered distinctive the two dorsolateral subdivisions; and 4) a dorsomedial region characterized by high kainate receptor density. We further observed similarities in receptor binding densities between subdivisions of the avian and mammalian HF. Despite the similarities, we propose that 300 hundred million years of independent evolution has led to a mosaic of similarities and differences in the organization of the avian HF and mammalian hippocampus and that thinking about the avian HF in terms of the strict organization of the mammalian hippocampus is likely insufficient to understand the HF of birds.
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The putative pigeon homologue to song bird LMAN does not modulate behavioral variability.
Behav. Brain Res.
PUBLISHED: 01-16-2014
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The active generation of behavioral variability is thought to be a pivotal element in reinforcement based learning. One example for this principle is song learning in oscine birds. Oscines possess a highly specialized set of brain areas that compose the song system. It is yet unclear how the song system evolved. One important hypothesis assumes a motor origin of the song system, i.e. the song system may have developed from motor pathways that were present in an early ancestor of extant birds. Indeed, in pigeons neural pathways are present that parallel the song system. We examined whether one component of these pathways, a forebrain area termed nidopallium intermedium medialis pars laterale (NIML), is functionally comparable to its putative homologue, the lateral magnocellular nucleus of the anterior nidopallium (LMAN) of the song system. LMAN conveys variability into the motor output during singing; a function crucial for song learning and maintenance. We tested if NIML is likewise associated with the generation of variability. We used a behavioral paradigm in which pigeons had to find hidden target areas on a touch screen to gain food rewards. Alterations in pecking variability would result in changes of performance levels in this search paradigm. We found that pharmacological inactivation of NIML did not reduce pecking variability contrasting increases of song stereotypy observed after LMAN inactivation.
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Oxytocin enhances brain reward system responses in men viewing the face of their female partner.
Proc. Natl. Acad. Sci. U.S.A.
PUBLISHED: 11-25-2013
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The biological mechanisms underlying long-term partner bonds in humans are unclear. The evolutionarily conserved neuropeptide oxytocin (OXT) is associated with the formation of partner bonds in some species via interactions with brain dopamine reward systems. However, whether it plays a similar role in humans has as yet not been established. Here, we report the results of a discovery and a replication study, each involving a double-blind, placebo-controlled, within-subject, pharmaco-functional MRI experiment with 20 heterosexual pair-bonded male volunteers. In both experiments, intranasal OXT treatment (24 IU) made subjects perceive their female partners face as more attractive compared with unfamiliar women but had no effect on the attractiveness of other familiar women. This enhanced positive partner bias was paralleled by an increased response to partner stimuli compared with unfamiliar women in brain reward regions including the ventral tegmental area and the nucleus accumbens (NAcc). In the left NAcc, OXT even augmented the neural response to the partner compared with a familiar woman, indicating that this finding is partner-bond specific rather than due to familiarity. Taken together, our results suggest that OXT could contribute to romantic bonds in men by enhancing their partners attractiveness and reward value compared with other women.
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The type of implicit motive enactment is modulated by sex hormones in naturally cycling women.
Physiol. Behav.
PUBLISHED: 09-11-2013
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Sex hormones have been reported to dynamically modulate the expression of implicit motives, a concept that has previously been thought to be relatively stable over time. This study investigates to what extent the need for affiliation, power, and achievement, as well as the form of enactment of these needs as measured with the Operant Motive Test (OMT), is affected by cycle-phase dependent sex hormone fluctuations. In addition to measuring the strength of motive expression, the OMT also captures different forms of motive enactment. In an intra-subject design with repeated measures, no evidence for cycle-phase related variation in overall motive scores was found. However, when different forms of motive enactment were considered, an effect of menstrual cycle was observed. The incentive-based inhibition of the power motive was significantly reduced at the time of ovulation, compared to the menstrual and to the mid-luteal phase, in naturally cycling women. In women with relatively stable hormone concentrations (due to using hormonal contraceptives), no significant changes in the form of motive enactment were evident. The results indicate a specific hormonal influence on motive-related cognitive processes that are related to inhibitive processes in behavior control.
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Selection for low mortality in laying hens affects catecholamine levels in the arcopallium, a brain area involved in fear and motor regulation.
Behav. Brain Res.
PUBLISHED: 08-13-2013
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Feather pecking (FP) in laying hens may cause mortality due to cannibalism. Novel breeding methods using survival days of group-housed siblings allow for the genetic selection of laying hens with low mortality (LML: low mortality line) due to cannibalism. Previous studies have demonstrated less fear-related behavior and also less FP in LML hens compared to CL. Selection also caused changes in locomotor behavior in an open field. It is unknown, however, whether selection for low mortality affects central neurotransmitter levels. In this study, brain monoamine levels were measured in the dorsal thalamus, medial striatum, hippocampus and arcopallium of adult laying hens of both LML and CL using HPLC. Brain samples were collected after 5-min of manual restraint. The most prominent line differences were found in the arcopallium. Compared to CL, LML had lower levels of noradrenaline (NA) and 3,4-dihydroxyphenylacetic acid (DOPAC) and tended to have lower levels of dopamine (DA), homovanillic acid (HVA), and 5-hydroxyindoleacetic acid (5-HIAA). Levels of serotonin (5-HT), 5-HT- and DA-turnover in this brain area were not affected by line. LML showed less fear-related behavior during the restraint than CL. These findings show that selection for low mortality in hens leads to changes of predominantly the dopaminergic system in the chickens arcopallium, a forebrain somatomotor area also related to fear. This suggests a relationship between catecholamine functioning in this brain area and FP and cannibalistic behavior in chickens and underpins previously found relationships between FP, fear and high activity.
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Handedness: A neurogenetic shift of perspective.
Neurosci Biobehav Rev
PUBLISHED: 06-27-2013
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Handedness is the single most studied aspect of human brain asymmetries. For long it has been thought to be a monogenic trait that can produce an asymmetrical shift of cerebral mechanisms, thereby producing right handedness. Nevertheless, a single gene explaining a sufficient amount of phenotypic variance has not been identified. The results of several recent studies using advanced molecular genetic techniques suggest that a multifactorial model taking into account both multiple genetic and environmental factors, as well as their interactions, might be better suited to explain the complex processes underlying the ontogenesis of handedness. In this article, we review the new insights into handedness genetics provided by these studies and discuss, how integrating results from genetic and neuroscientific studies might help us to generate more accurate models of the ontogenesis of handedness. Based on these thoughts, we suggest several candidate gene groups (e.g. genes involved in the formation of the corpus callosum, asymmetrically expressed genes or genes involved in the development of structural left-right asymmetries) whose investigation would help to further understand the complex relation of genes, the brain and handedness.
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FOXP2 variation modulates functional hemispheric asymmetries for speech perception.
Brain Lang
PUBLISHED: 06-24-2013
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Left-hemispheric language dominance is a well-known characteristic of the human language system, but the molecular mechanisms underlying this crucial feature of vocal communication are still far from being understood. The forkhead box P2 gene FOXP2, which has been related to speech development, constitutes an interesting candidate gene in this regard. Therefore, the present study was aimed at investigating effects of variation in FOXP2 on individual language dominance. To this end, we used a dichotic listening and a visual half-field task in a sample of 456 healthy adults. The FOXP2 SNPs rs2396753 and rs12533005 were found to be significantly associated with the distribution of correct answers on the dichotic listening task. These results show that variation in FOXP2 may contribute to the inter-individual variability in hemispheric asymmetries for speech perception.
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The rubber hand illusion in complex regional pain syndrome: preserved ability to integrate a rubber hand indicates intact multisensory integration.
Pain
PUBLISHED: 03-09-2013
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In patients with complex regional pain syndrome (CRPS) type 1, processing of static tactile stimuli is impaired, whereas more complex sensory integration functions appear preserved. This study investigated higher order multisensory integration of body-relevant stimuli using the rubber hand illusion in CRPS patients. Subjective self-reports and skin conductance responses to watching the rubber hand being harmed were compared among CRPS patients (N=24), patients with upper limb pain of other origin (N=21, clinical control group), and healthy subjects (N=24). Additionally, the influence of body representation (body plasticity [Trinity Assessment of Body Plasticity], neglect-like severity symptoms), and clinical signs of illusion strength were investigated. For statistical analysis, 1-way analysis of variance, t test, Pearson correlation, with ?=0.05 were used. CRPS patients did not differ from healthy subjects and the control group with regard to their illusion strength as assessed by subjective reports or skin conductance response values. Stronger left-sided rubber hand illusions were reported by healthy subjects and left-side-affected CRPS patients. Moreover, for this subgroup, illness duration and illusion strength were negatively correlated. Overall, severity of neglect-like symptoms and clinical signs were not related to illusion strength. However, patients with CRPS of the right hand reported significantly stronger neglect-like symptoms and significantly lower illusion strength of the affected hand than patients with CRPS of the left hand. The weaker illusion of CRPS patients with strong neglect-like symptoms on the affected hand supports the role of top-down processes modulating body ownership. Moreover, the intact ability to perceive illusory ownership confirms the notion that, despite impaired processing of proprioceptive or tactile input, higher order multisensory integration is unaffected in CRPS.
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Suboptimal criterion setting in a perceptual choice task with asymmetric reinforcement.
Behav. Processes
PUBLISHED: 02-18-2013
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Performance on psychophysical tasks is influenced by a variety of non-sensory factors, most notably the magnitude or probability of reinforcement following correct responses. When reinforcement probability is unequal for hits and correct rejections, signal detection theory specifies an optimal decision criterion which maximizes the number of reinforcers. We subjected pigeons to a task in which six different stimuli (shades of gray) had to be assigned to one of two categories. Animals were confronted with asymmetric reinforcement schedules in which correct responses to five of the stimuli were reinforced with a probability of 0.5, while correct responses to the remaining stimulus were extinguished. The subjects resultant choice probabilities clearly deviated from those predicted by a maximization account. More specifically, the magnitude of the choice bias increased with the distance of the to-be-extinguished stimulus to the category boundary, a pattern opposite to that posited by maximization. The present and a previous set of results in which animals performed optimally can be explained by a simple choice mechanism in which a variable decision criterion is constantly updated according to a leaky integration of incomes attained from both response options.
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Stimulus-response-outcome coding in the pigeon nidopallium caudolaterale.
PLoS ONE
PUBLISHED: 01-21-2013
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A prerequisite for adaptive goal-directed behavior is that animals constantly evaluate action outcomes and relate them to both their antecedent behavior and to stimuli predictive of reward or non-reward. Here, we investigate whether single neurons in the avian nidopallium caudolaterale (NCL), a multimodal associative forebrain structure and a presumed analogue of mammalian prefrontal cortex, represent information useful for goal-directed behavior. We subjected pigeons to a go-nogo task, in which responding to one visual stimulus (S+) was partially reinforced, responding to another stimulus (S-) was punished, and responding to test stimuli from the same physical dimension (spatial frequency) was inconsequential. The birds responded most intensely to S+, and their response rates decreased monotonically as stimuli became progressively dissimilar to S+; thereby, response rates provided a behavioral index of reward expectancy. We found that many NCL neurons responses were modulated in the stimulus discrimination phase, the outcome phase, or both. A substantial fraction of neurons increased firing for cues predicting non-reward or decreased firing for cues predicting reward. Interestingly, the same neurons also responded when reward was expected but not delivered, and could thus provide a negative reward prediction error or, alternatively, signal negative value. In addition, many cells showed motor-related response modulation. In summary, NCL neurons represent information about the reward value of specific stimuli, instrumental actions as well as action outcomes, and therefore provide signals useful for adaptive behavior in dynamically changing environments.
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Cholecystokinin A receptor (CCKAR) gene variation is associated with language lateralization.
PLoS ONE
PUBLISHED: 01-14-2013
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Schizophrenia is a psychiatric disorder associated with atypical handedness and language lateralization. However, the molecular mechanisms underlying these functional changes are still poorly understood. Therefore, the present study was aimed at investigating whether variation in schizophrenia-related genes modulates individual lateralization patterns. To this end, we genotyped 16 single nucleotide polymorphisms that have previously been linked to schizophrenia on a meta-analysis level in a sample of 444 genetically unrelated healthy participants and examined the association of these polymorphisms with handedness, footedness and language lateralization. We found a significant association of the cholecystokinin-A receptor (CCKAR) gene variation rs1800857 and language lateralization assessed using the dichotic listening task. Individuals carrying the schizophrenia risk allele C of this polymorphism showed a marked reduction of the typical left-hemispheric dominance for language processing. Since the cholecystokinin A receptor is involved in dopamine release in the central nervous system, these findings suggest that genetic variation in this receptor may modulate language lateralization due to its impact on dopaminergic pathways.
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Variability in ratings of trustworthiness across the menstrual cycle.
Biol Psychol
PUBLISHED: 01-10-2013
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This study investigated how trusting behavior varies in naturally cycling women, as a function of sex and attractiveness of players in a trust game, at three distinct phases of the menstrual cycle. Women acted more cautiously in an investment game at the preovulatory phase, compared to the menstrual and the mid-luteal phase. Reduced willingness to trust in strangers was particularly expressed toward male players at this time. The increase of estradiol levels from menses to the preovulatory phase was negatively correlated with trust in attractive male other players, whereas the increase of progesterone levels from menses to the mid-luteal phase was positively associated with trust in unattractive female other players. No particular contribution of a single hormone level could be identified for the generally reduced willingness to trust in strangers in the preovulatory phase. Thus, the results emphasize the impact of the menstrual cycle on interpersonal trust, although the exact mode of hormonal action needs to be further investigated.
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Response inhibition is modulated by functional cerebral asymmetries for facial expression perception.
Front Psychol
PUBLISHED: 01-01-2013
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The efficacy of executive functions is critically modulated by information processing in earlier cognitive stages. For example, initial processing of verbal stimuli in the language-dominant left-hemisphere leads to more efficient response inhibition than initial processing of verbal stimuli in the non-dominant right hemisphere. However, it is unclear whether this organizational principle is specific for the language system, or a general principle that also applies to other types of lateralized cognition. To answer this question, we investigated the neurophysiological correlates of early attentional processes, facial expression perception and response inhibition during tachistoscopic presentation of facial "Go" and "Nogo" stimuli in the left and the right visual field (RVF). Participants committed fewer false alarms after Nogo-stimulus presentation in the left compared to the RVF. This right-hemispheric asymmetry on the behavioral level was also reflected in the neurophysiological correlates of face perception, specifically in a right-sided asymmetry in the N170 amplitude. Moreover, the right-hemispheric dominance for facial expression processing also affected event-related potentials typically related to response inhibition, namely the Nogo-N2 and Nogo-P3. These findings show that an effect of hemispheric asymmetries in early information processing on the efficacy of higher cognitive functions is not limited to left-hemispheric language functions, but can be generalized to predominantly right-hemispheric functions.
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Multisensory integration across the menstrual cycle.
Front Psychol
PUBLISHED: 01-01-2013
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Evidence suggests that spatial processing changes across time in naturally cycling women, which is likely due to neuromodulatory effects of steroid hormones. Yet, it is unknown whether crossmodal spatial processes depend on steroid hormones as well. In the present experiment, the crossmodal congruency task was used to assess visuo-tactile interactions in naturally cycling women, women using hormonal contraceptives and men. Participants adopted either a crossed or uncrossed hands posture. It was tested whether a postural effect of hand crossing on multisensory interactions in the crossmodal congruency task is modulated by womens cycle phase. We found that visuotactile interactions changed according to cycle phase. Naturally cycling women showed a significant difference between the menstrual and the luteal phase for crossed, but not for uncrossed hands postures. The two control groups showed no test sessions effects. Regression analysis revealed a positive relation between estradiol levels and the size of crossmodal congruency effects (CCE), indicating that estradiol seems to have a neuromodulatory effect on posture processing.
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Large-scale network organization in the avian forebrain: a connectivity matrix and theoretical analysis.
Front Comput Neurosci
PUBLISHED: 01-01-2013
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Many species of birds, including pigeons, possess demonstrable cognitive capacities, and some are capable of cognitive feats matching those of apes. Since mammalian cortex is laminar while the avian telencephalon is nucleated, it is natural to ask whether the brains of these two cognitively capable taxa, despite their apparent anatomical dissimilarities, might exhibit common principles of organization on some level. Complementing recent investigations of macro-scale brain connectivity in mammals, including humans and macaques, we here present the first large-scale "wiring diagram" for the forebrain of a bird. Using graph theory, we show that the pigeon telencephalon is organized along similar lines to that of a mammal. Both are modular, small-world networks with a connective core of hub nodes that includes prefrontal-like and hippocampal structures. These hub nodes are, topologically speaking, the most central regions of the pigeons brain, as well as being the most richly connected, implying a crucial role in information flow. Overall, our analysis suggests that indeed, despite the absence of cortical layers and close to 300 million years of separate evolution, the connectivity of the avian brain conforms to the same organizational principles as the mammalian brain.
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PCSK6 VNTR Polymorphism Is Associated with Degree of Handedness but Not Direction of Handedness.
PLoS ONE
PUBLISHED: 01-01-2013
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Although the left and right human cerebral hemispheres differ both functionally and anatomically, the mechanisms that underlie the establishment of these hemispheric specializations, as well as their physiological and behavioral implications, remain largely unknown. Since cerebral asymmetry is strongly correlated with handedness, and handedness is assumed to be influenced by a number of genetic and environmental factors, we performed an association study of LRRTM1 rs6733871 and a number of polymorphisms in PCSK6 and different aspects of handedness assessed with the Edinburgh handedness inventory in a sample of unrelated healthy adults (n?=?1113). An intronic 33bp variable-number tandem repeat (VNTR) polymorphism in PCSK6 (rs10523972) shows a significant association (significance threshold: p<0.0025, adjusted for multiple comparisons) with a handedness category comparison (P?=?0.0005) and degree of handedness (P?=?0.001). These results provide further evidence for the role of PCSK6 as candidate for involvement in the biological mechanisms that underlie the establishment of normal brain lateralization and thus handedness and support the assumption that the degree of handedness, instead the direction, may be the more appropriate indicator of cerebral organization.
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Brain activation in motor sequence learning is related to the level of native cortical excitability.
PLoS ONE
PUBLISHED: 01-01-2013
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Cortical excitability may be subject to changes through training and learning. Motor training can increase cortical excitability in motor cortex, and facilitation of motor cortical excitability has been shown to be positively correlated with improvements in performance in simple motor tasks. Thus cortical excitability may tentatively be considered as a marker of learning and use-dependent plasticity. Previous studies focused on changes in cortical excitability brought about by learning processes, however, the relation between native levels of cortical excitability on the one hand and brain activation and behavioral parameters on the other is as yet unknown. In the present study we investigated the role of differential native motor cortical excitability for learning a motor sequencing task with regard to post-training changes in excitability, behavioral performance and involvement of brain regions. Our motor task required our participants to reproduce and improvise over a pre-learned motor sequence. Over both task conditions, participants with low cortical excitability (CElo) showed significantly higher BOLD activation in task-relevant brain regions than participants with high cortical excitability (CEhi). In contrast, CElo and CEhi groups did not exhibit differences in percentage of correct responses and improvisation level. Moreover, cortical excitability did not change significantly after learning and training in either group, with the exception of a significant decrease in facilitatory excitability in the CEhi group. The present data suggest that the native, unmanipulated level of cortical excitability is related to brain activation intensity, but not to performance quality. The higher BOLD mean signal intensity during the motor task might reflect a compensatory mechanism in CElo participants.
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Lateralisation of conspecific vocalisation in non-human vertebrates.
Laterality
PUBLISHED: 12-09-2011
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Lateralisation of conspecific vocalisation has been observed in several vertebrate species. In the present article we review the results of behavioural and neuroanatomical studies investigating this feature. By employing cladographic comparisons we identify those vertebrate orders in which evidence for or against lateralisation of production and perception of conspecific vocalisation has been reported, and those orders in which further research is necessary. The analysis shows that there is evidence for lateralisation of conspecific vocalisation in several mammalian orders (e.g., Primates) and also evidence for lateralisation of conspecific vocalisation in some avian species (e.g., within the Passeriformes order). While the primate data in particular suggest that human language lateralisation could have resulted from an inherited dominance of the left hemisphere for those neural properties of language that are shared with the sensory or motor aspects of vocalisations in other vertebrate species, it becomes clear that this conclusion is presently supported by only sparse empirical evidence. The majority of vertebrate orders, especially among non-amniotes, still need to be explored.
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Hemispheric asymmetries and cognitive flexibility: an ERP and sLORETA study.
Brain Cogn
PUBLISHED: 06-28-2011
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Although functional cerebral asymmetries (FCAs) affect all cognitive domains, their modulation of the efficacy of specific executive functions is largely unexplored. In the present study, we used a lateralized version of the task switching paradigm to investigate the relevance of hemispheric asymmetries for cognitive control processes. Words were tachistoscopically presented in the left (LVF) and right visual half field (RVF). Participants had to categorise the words either based on their initial letters, or according to their word type. On half of the trials the task changed (switch trials) whereas on the other half it stayed the same (repeat trials). ERPs were recorded and the neural sources of the ERPs were reconstructed using standardised low resolution brain electromagnetic tomography (sLORETA). In the word type task, participants were faster on repeat trials when stimuli were presented in the RVF. In contrast, in the initial letter task participants were faster on repeat trials and in general more accurate after stimulus presentation in the LVF. In both tasks, no hemispheric asymmetries in reaction times were observed on switch trials. On the electrophysiological level, we observed a left lateralization of the N1 that was mediated by activation in the left extrastriate cortex as well as a greater positivity of the P3b after stimulus presentation in the RVF compared to the LVF that was mediated by activation in the superior parietal cortex. These results show that FCAs affect the neurophysiological correlates of executive functions related to task switching. The relation of neurophysiological and behavioural asymmetries is mediated by task complexity, with more complex tasks leading to more interhemispheric interaction and smaller left-right differences in behavioural measures. These findings reveal that FCAs are an important modulator of executive functions related to cognitive flexibility.
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Visuotactile interactions in the congenitally acallosal brain: evidence for early cerebral plasticity.
Neuropsychologia
PUBLISHED: 06-15-2011
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Studies in patients with an isolated, congenital agenesis of the corpus callosum have documented potentials and limits of brain plasticity. Literature suggests that early reorganization mechanisms can compensate for the absence of the corpus callosum in unisensory tasks that involve interhemispheric transfer. It is unknown, however, how the congenitally acallosal brain processes multisensory information, which presumably requires interhemispheric transfer of modality-specific input. Therefore, we tested five patients with total and one patient with partial agenesis of the corpus callosum in a visuotactile interference task (the "crossmodal congruency task") with uncrossed and crossed hands and compared their performance to that of 31 healthy controls. We found that congruency effects followed the hands in space not only in healthy, but also in congenitally acallosal individuals. Remarkably, this was also true when patients hands crossed the vertical visual meridian and stimuli were presented at the same hand. These results suggest that callosal connectivity is not required for remapping of visuotactile space. We conclude that early brain plasticity allows for compensation of the developmental absence of the corpus callosum in a visuotactile interference task.
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Variation in the NMDA receptor 2B subunit gene GRIN2B is associated with differential language lateralization.
Behav. Brain Res.
PUBLISHED: 05-31-2011
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Variations in the N-methyl-d-aspartate receptor 2B subunit gene (GRIN2B) have been associated with schizophrenia, a psychiatric disorder associated with reduced left-hemispheric language dominance. Here, we investigated, whether different polymorphisms in GRIN2B influence language lateralization and handedness in healthy individuals. In a cohort of 424 genetically unrelated participants we found significant association between the synonymous GRIN2B variation rs1806201 and language lateralization assessed using the dichotic listening task. Individuals carrying the heterozygous CT genotype exhibited more pronounced left-hemispheric language dominance as compared to both homozygous CC and TT individuals. Such an association was not identified for handedness. These findings suggest that variation in NMDA-receptors contributes to the interindividual variability of language lateralization.
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The motor side of emotions: investigating the relationship between hemispheres, motor reactions and emotional stimuli.
Psychol Res
PUBLISHED: 04-12-2011
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The aim of the present study was to analyze if the left hemisphere preferentially controls flexion responses toward positive stimuli, while the right hemisphere is specialized toward extensor responses to negative pictures. To this end, right-handed subjects had to pull or push a joystick subsequent to seeing a positive or a negative stimulus in their left or right hemifield. Flexion responses were faster for positive stimuli, while negative stimuli were associated with faster extensions responses. Overall, performance was fastest when emotional stimuli were presented to the left visual hemifield. This right hemisphere superiority was especially clear for negative stimuli, while reaction times toward positive pictures showed no hemispheric difference. We did not find any interaction between hemifield and response type. Neither was there a triple interaction between valence, hemifield and response type. We suppose that response dichotomies in humans are not as tightly linked to a hemisphere- and valence-bound reaction type as previously assumed.
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The convergent evolution of neural substrates for cognition.
Psychol Res
PUBLISHED: 03-17-2011
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This review describes a case of convergence in the evolution of brain and cognition. Both mammals and birds can organize their behavior flexibly over time and evolved similar cognitive skills. The avian forebrain displays no lamination that corresponds to the mammalian neocortex; hence, lamination does not seem to be a requirement for higher cognitive functions. In mammals, executive functions are associated with the prefrontal cortex. The corresponding structure in birds is the nidopallium caudolaterale. Anatomic, neurochemical, electrophysiologic and behavioral studies show these structures to be highly similar, but not homologous. Thus, despite the presence (mammals) or the absence (birds) of a laminated forebrain, prefrontal areas in mammals and birds converged over evolutionary time into a highly similar neural architecture. The neuroarchitectonic degrees of freedom to create different neural architectures that generate identical prefrontal functions seem to be very limited.
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Smoking reduces language lateralization: a dichotic listening study with control participants and schizophrenia patients.
Brain Cogn
PUBLISHED: 02-13-2011
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Schizophrenia has been associated with deficits in functional brain lateralization. According to some authors, the reduction of asymmetry could even promote this psychosis. At the same time, schizophrenia is accompanied by a high prevalence of nicotine dependency compared to any other population. This association is very interesting, because sex-dependent effects of smoking in auditory language asymmetries have been reported recently, and the verbal domain is also one major focus in cognitive deficit studies of schizophrenia. Thus, the altered laterality pattern in schizophrenia could, at least in part, result from secondary artefacts due to smoking rather than being a pure cause of the disease itself. To test this hypothesis, the present study examined auditory language lateralization in 67 schizophrenia patients and in 72 healthy controls in a phonemic and an emotional dichotic listening task. Our findings replicate previous research, in that smoking reduces language lateralization in men in phonemic dichotic listening. In addition, we show that smoking also reduces laterality in women in the emotional dichotic listening task. Thus, smoking alters phonemic and emotional language asymmetries differentially for men and women, with a stronger effect for men in the left hemisphere phonemic task, and a stronger effect for women in the right hemisphere emotional task. Together, these findings point towards an effect of smoking which is possibly independent of sex and hemisphere. Importantly, by testing equal numbers of smoking and non-smoking patients and controls, we found no schizophrenia-associated asymmetry effect. Possible neurobiological mechanisms with which smoking may alter auditory microcircuits and thereby diminish left-right differences are discussed.
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Improvement and impairment of visually guided behavior through LTP- and LTD-like exposure-based visual learning.
Curr. Biol.
PUBLISHED: 01-31-2011
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Cellular studies have focused on long-term potentiation (LTP) and long-term depression (LTD) to understand requirements for persistent changes in synaptic connections. Whereas LTP is induced through high-frequency intermittent stimulation, low-frequency stimulation evokes LTD. Because of the ubiquitous efficacy of these protocols, they are considered fundamental mechanisms underlying learning. Here we adapted LTP/LTD-like protocols to visual stimulation to alter human visually guided behavior. In a change-detection task, participants reported luminance changes against distracting orientation changes. Subsequently, they were exposed to passive visual high- or low-frequency stimulation of either the relevant luminance or irrelevant orientation feature. LTP-like high-frequency protocols using luminance improved ability to detect luminance changes, whereas low-frequency LTD-like stimulation impaired performance. In contrast, LTP-like exposure of the irrelevant orientation feature impaired performance, whereas LTD-like orientation stimulation improved it. LTP-like effects were present for 10 days, whereas LTD-like effects lasted for a shorter period of time. Our data demonstrate that instead of electrically stimulating synapses, selective behavioral changes are evoked in humans by using equivalently timed visual stimulation, suggesting that both LTD- and LTP-like protocols control human behavior but that the direction of changes is determined by the feature incorporated into the stimulation protocol.
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Adaptive criterion setting in perceptual decision making.
J Exp Anal Behav
PUBLISHED: 01-28-2011
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Pigeons responded in a perceptual categorization task with six different stimuli (shades of gray), three of which were to be classified as "light" or "dark", respectively. Reinforcement probability for correct responses was varied from 0.2 to 0.6 across blocks of sessions and was unequal for correct light and dark responses. Introduction of a new reinforcement contingency resulted in a biphasic process of adjustment: First, choices were strongly biased towards the favored alternative, which was followed by a shift of preference back towards unbiased choice allocation. The data are well described by a signal detection model in which adjustment to a change in reinforcement contingency is modeled as the change of a criterion along a decision axis with fixed stimulus distributions. Moreover, the model shows that pigeons, after an initial overadjustment, distribute their responses almost optimally, although the overall benefit from doing so is extremely small. The strong and swift effect of minute changes in overall reinforcement probability precludes a choice strategy directly maximizing expected value, contrary to the assumption of signal detection theory. Instead, the rapid adjustments observed can be explained by a model in which reinforcement probabilities for each action, contingent on perceived stimulus intensity, determine choice allocation.
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The receptor architecture of the pigeons nidopallium caudolaterale: an avian analogue to the mammalian prefrontal cortex.
Brain Struct Funct
PUBLISHED: 01-12-2011
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The avian nidopallium caudolaterale is a multimodal area in the caudal telencephalon that is apparently not homologous to the mammalian prefrontal cortex but serves comparable functions. Here we analyzed binding-site densities of glutamatergic AMPA, NMDA and kainate receptors, GABAergic GABA(A), muscarinic M(1), M(2) and nicotinic (nACh) receptors, noradrenergic ?(1) and ?(2), serotonergic 5-HT(1A) and dopaminergic D(1)-like receptors using quantitative in vitro receptor autoradiography. We compared the receptor architecture of the pigeons nidopallial structures, in particular the NCL, with cortical areas Fr2 and Cg1 in rats and prefrontal area BA10 in humans. Our results confirmed that the relative ratios of multiple receptor densities across different nidopallial structures (their "receptor fingerprints") were very similar in shape; however, the absolute binding densities (the "size" of the fingerprints) differed significantly. This finding enables a delineation of the avian NCL from surrounding structures and a further parcellation into a medial and a lateral part as revealed by differences in densities of nACh, M(2), kainate, and 5-HT(1A) receptors. Comparisons of the NCL with the rat and human frontal structures showed differences in the receptor distribution, particularly of the glutamate receptors, but also revealed highly conserved features like the identical densities of GABA(A), M(2), nACh and D(1)-like receptors. Assuming a convergent evolution of avian and mammalian prefrontal areas, our results support the hypothesis that specific neurochemical traits provide the molecular background for higher order processes such as executive functions. The differences in glutamate receptor distributions may reflect species-specific adaptations.
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Lateralized neural mechanisms underlying the modulation of response inhibition processes.
Neuroimage
PUBLISHED: 01-11-2011
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Functional cerebral asymmetries (FCAs) are an important modulator of cognitive functions. Here, we investigated the temporal and spectral dynamics as well as the cortical networks underlying the lateralized modulation of executive functions related to response inhibition. To this end, we recorded event-related potentials (ERPs) during tachistoscopic presentation of verbal Go and Nogo stimuli in the left (LVF) and the right visual field (RVF). Participants committed fewer false alarms to verbal Nogo stimuli presented in the RVF than to stimuli presented in the LVF. This asymmetry was paralleled by neurophysiological data. The Nogo-N2 and related delta frequency band power were stronger when response inhibition was driven by stimuli presented in the LVF, implying a stronger response conflict. This effect was mediated by stronger activations in bilateral medial-prefrontal and especially left parietal networks. This shows that asymmetries in behavioural performance do not necessarily reflect differences in the overall capability of one hemisphere to solve a task. Even though information is initially confined to one hemisphere after tachistoscopic presentation, this does not primarily cause behavioural asymmetries. Instead, hemispheric dominances in information processing can induce differences in demands on cognitive processes operating via bilateral networks that ultimately drive behavioural asymmetries.
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Visual processing asymmetries in change detection.
Perception
PUBLISHED: 08-12-2010
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Change detection is critically dependent on attentional mechanisms. However, the relation between an asymmetrical distribution of visuo-spatial attention and the detection of changes in visual scenes is not clear. Spatial tasks are known to induce a stronger activation of the right hemisphere. The effects of such visual processing asymmetries induced by a spatial task on change detection were investigated. When required to detect changes in the left and in the right visual fields, participants were significantly faster in detecting changes on the left than on the right. Importantly, this left-side superiority in change detection is not influenced by inspection time, suggesting a critical role of visual processing benefit for the left visual field.
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Interaction of magnetite-based receptors in the beak with the visual system underlying fixed direction responses in birds.
Front. Zool.
PUBLISHED: 06-07-2010
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European robins, Erithacus rubecula, show two types of directional responses to the magnetic field: (1) compass orientation that is based on radical pair processes and lateralized in favor of the right eye and (2) so-called fixed direction responses that originate in the magnetite-based receptors in the upper beak. Both responses are light-dependent. Lateralization of the fixed direction responses would suggest an interaction between the two magnetoreception systems.
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Navigation-induced ZENK expression in the olfactory system of pigeons (Columba livia).
Eur. J. Neurosci.
PUBLISHED: 05-31-2010
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A large body of evidence indicates that pigeons use olfactory cues to navigate over unfamiliar areas with a differential contribution of the left and right hemispheres. In particular, the right nostril/olfactory bulb (OB) and left piriform cortex (Cpi) have been demonstrated to be crucially involved in navigation. In this study we analysed behaviour-induced activation of the olfactory system, indicated by the expression of the immediate early gene ZENK, under different homing conditions. One experimental group was released from an unfamiliar site, the second group was transported to the unfamiliar site and back to the loft, and the third group was released in front of the loft. To evaluate the differential contribution of the left and/or right olfactory input, the nostrils of the pigeons were either occluded unilaterally or not. Released pigeons revealed the highest ZENK cell density in the OB and Cpi, indicating that the olfactory system is activated during navigation from an unfamiliar site. The groups with no plug showed the highest ZENK cell density, supporting the activation of the olfactory system probably being due to sensory input. Moreover, both Cpis seem to contribute differently to the navigation process. Only occlusion of the right OB resulted in a decreased ZENK cell expression in the Cpi, whereas occlusion of the left nostril had no effect. This is the first study to reveal neuronal activation patterns in the olfactory system during homing. Our data show that lateralized processing of olfactory cues is indeed involved in navigation over unfamiliar areas.
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Double dissociated effects of the functional TNF-? -308G/A polymorphism on processes of cognitive control.
Neuropsychologia
PUBLISHED: 05-21-2010
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Neuroimmunological factors may modulate brain functions and are important to understand the molecular basis of cognition. The tumor necrosis factor alpha (TNF-?) is known to induce neurodegenerative changes in the basal ganglia, but the cognitive effects of these changes are not understood. Since the basal ganglia are neurobiologically heterogeneous, different cognitive functions mediated by basal ganglia-prefrontal loops (response inhibition and error processing) may not necessarily be uniformly affected. Response inhibition and error processing functions were examined using event-related potentials (ERPs) and subjects (N=71) were genotyped for the functional TNF-? -308G?A polymorphism. We show a double-dissociated effect of the functional TNF-? -308G?A polymorphism on response inhibition and error processing. While response inhibition functions were more effective in the AA/AG genotype group, error monitoring functions are adversely affected in this genotype group. In the GG genotype group, the pattern of results was vice versa. The results refine the view of the effects of TNF-? on cognitive functions.
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Dominant vertical orientation processing without clustered maps: early visual brain dynamics imaged with voltage-sensitive dye in the pigeon visual Wulst.
J. Neurosci.
PUBLISHED: 05-14-2010
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The pigeon is a widely established behavioral model of visual cognition, but the processes along its most basic visual pathways remain mostly unexplored. Here, we report the neuronal population dynamics of the visual Wulst, an assumed homolog of the mammalian striate cortex, captured for the first time with voltage-sensitive dye imaging. Responses to drifting gratings were characterized by focal emergence of activity that spread extensively across the entire Wulst, followed by rapid adaptation that was most effective in the surround. Using additional electrophysiological recordings, we found cells that prefer a variety of orientations. However, analysis of the imaged spatiotemporal activation patterns revealed no clustered orientation map-like arrangements as typically found in the primary visual cortices of many mammalian species. Instead, the vertical orientation was overrepresented, both in terms of the imaged population signal, as well as the number of neurons preferring the vertical orientation. Such enhanced selectivity for the vertical orientation may result from horizontal motion vectors that trigger adaptation to the extensive flow field input during natural behavior. Our findings suggest that, although the avian visual Wulst is homologous to the primary visual cortex in terms of its gross anatomical connectivity and topology, its detailed operation and internal organization is still shaped according to specific input characteristics.
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Magnetoreception of directional information in birds requires nondegraded vision.
Curr. Biol.
PUBLISHED: 04-07-2010
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The magnetic compass orientation of birds is light dependent. The respective directional information, originating in radical pair processes, is mediated by the right eye. These findings suggest possible interactions between magnetoreception and vision, in particular with the perception of contours, because the right eye has been found to be dominant in discrimination tasks requiring object vision. Here we report tests in the local geomagnetic field with European robins wearing goggles equipped with a clear and a frosted foil of equal translucence of 70%. Robins with a clear foil on the right eye and a frosted foil on the left eye oriented in the migratory direction as well as birds using both eyes. Birds with a frosted foil that blurred vision on the right eye and a clear foil on the left eye, in contrast, were disoriented. These findings are the first to show that avian magnetoreception requires, in addition to light, a nondegraded image formation along the projectional streams of the right retina. This suggests crucial interactions between the processing of visual pattern information and the conversion of magnetic input into directional information.
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Tool-making new caledonian crows have large associative brain areas.
Brain Behav. Evol.
PUBLISHED: 03-09-2010
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Animals with a high rate of innovative and associative-based behavior usually have large brains. New Caledonian (NC) crows stand out due to their tool manufacture, their generalized problem-solving abilities and an extremely high degree of encephalization. It is generally assumed that this increased brain size is due to the ability to process, associate and memorize diverse stimuli, thereby enhancing the propensity to invent new and complex behaviors in adaptive ways. However, this premise lacks firm empirical support since encephalization could also result from an increase of only perceptual and/or motor areas. Here, we compared the brain structures of NC crows with those of carrion crows, jays and sparrows. The brains of NC crows were characterized by a relatively large mesopallium, striatopallidal complex, septum and tegmentum. These structures mostly deal with association and motor-learning. This supports the hypothesis that the evolution of innovative or complex behavior requires a brain composition that increases the ability to associate and memorize diverse stimuli in order to execute complex motor output. Since apes show a similar correlation of cerebral growth and cognitive abilities, the evolution of advanced cognitive skills appears to have evolved independently in birds and mammals but with a similar neural orchestration.
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Laterality in the rubber hand illusion.
Laterality
PUBLISHED: 03-01-2010
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In patient studies, impairments of sense of body ownership have repeatedly been linked to right-hemispheric brain damage. To test whether a right-hemispheric dominance for sense of body ownership could also be observed in healthy adults, the rubber hand illusion was elicited on both hands of 21 left-handers and 22 right-handers. In this illusion, a participants real hand is stroked while hidden from view behind an occluder, and a nearby visible hand prosthesis is repeatedly stroked in synchrony. Most participants experience the illusionary perception of touch sensations arising from the prosthesis. The vividness of the illusion was measured by subjective self-reports as well as by skin conductance responses to watching the rubber hand being harmed. Handedness did not affect the vividness of the illusion, but a stronger skin conductance response was observed, when the illusion was elicited on the left hand. These findings suggest a right-hemispheric dominance for sense of body ownership in healthy adults.
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Smoking modulates language lateralization in a sex-specific way.
Neuropsychologia
PUBLISHED: 01-09-2010
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Smoking affects a widespread network of neuronal functions by altering the properties of acetylcholinergic transmission. Recent studies show that nicotine consumption affects ascending auditory pathways and alters auditory attention, particularly in men. Here we show that smoking affects language lateralization in a sex-specific way. We assessed brain asymmetries of 90 healthy, right-handed participants using a classic consonant-vowel syllable dichotic listening paradigm in a 2×3 experimental design with sex (male, female) and smoking status (non-smoker, light smoker, heavy smoker) as between-subject factors. Our results revealed that male smokers had a significantly less lateralized response pattern compared to the other groups due to a decreased response rate of their right ear. This finding suggests a group-specific impairment of the speech dominant left hemisphere. In addition, decreased overall response accuracy was observed in male smokers compared to the other experimental groups. Similar adverse effects of smoking were not detected in women. Further, a significant negative correlation was detected between the severity of nicotine dependency and response accuracy in male but not in female smokers. Taken together, these results show that smoking modulates functional brain lateralization significantly and in a sexually dimorphic manner. Given that some psychiatric disorders have been associated with altered brain asymmetries and increased smoking prevalence, nicotinergic effects need to be specifically investigated in this context in future studies.
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Lateralization of magnetic compass orientation in pigeons.
J R Soc Interface
PUBLISHED: 01-06-2010
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The aim of our study was to test for lateralization of magnetic compass orientation in pigeons. Having shown that pigeons are capable of learning magnetic compass directions in an operant task, we wanted to know whether the brain hemispheres contribute differently and how the lateralization pattern relates to findings in other avian species. Birds that had learnt to locate food in an operant chamber by means of magnetic directions were tested for lateralization of magnetic compass orientation by temporarily covering one eye. Successful orientation occurred under all conditions of viewing. Thus, pigeons can perceive and process magnetic compass directions with the right eye and left brain hemisphere as well as the left eye and right brain hemisphere. However, while the right brain hemisphere tended to confuse the learned direction with its opposite (axial response), the left brain hemisphere specifically preferred the correct direction. Our findings demonstrate bilateral processing of magnetic information, but also suggest qualitative differences in how the left and the right brain deal with magnetic cues.
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Sex differences in parking are affected by biological and social factors.
Psychol Res
PUBLISHED: 09-04-2009
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The stereotype of womens limited parking skills is deeply anchored in modern culture. Although laboratory tests prove mens average superiority in visuospatial tasks and parking requires complex, spatial skills, underlying mechanisms remain unexplored. Here, we investigated performance of beginners (nine women, eight men) and more experienced drivers (21 women, 27 men) at different parking manoeuvres. Furthermore, subjects conducted the mental rotation test and self-assessed their parking skills. We show that men park more accurately and especially faster than women. Performance is related to mental rotation skills and self-assessment in beginners, but only to self-assessment in more experienced drivers. We assume that, due to differential feedback, self-assessment incrementally replaces the controlling influence of mental rotation, as parking is trained with increasing experience. Results suggest that sex differences in spatial cognition persist in real-life situations, but that socio-psychological factors modulate the biological causes of sex differences.
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Visual experience affects handedness.
Behav. Brain Res.
PUBLISHED: 08-15-2009
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In birds, a lateralised visual input during early development importantly modulates morphological and functional asymmetries of vision. We tested the hypothesis that human handedness similarly results from a combination of inborn and experience-driven factors by analysing sidedness in children suffering from congenital muscular torticollis. These children display a permanently tilted asymmetric head posture to the left or to the right in combination with a contralateral rotation of face and chin, which could lead to an increased visual experience of the hand contralateral to the head-tilt. Relative to controls, torticollis-children had a higher probability of right- or left-handedness when having a head-tilt to the opposite side. No statistical significant relation between head position and direction of functional asymmetries was found for footedness and eye-preference, although the means show a non-significant trend in the same direction as was observed for handedness. Thus, an increased visual control of the hand during early childhood seems to modulate handedness and possibly other lateral preferences to a lesser extent. These findings not only show that human handedness is affected by early lateralised visual experience but also speak in favour of a combined gene-environment model for its development.
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Visual asymmetries in Japanese quail (Coturnix japonica) retain a lifelong potential for plasticity.
Behav. Neurosci.
PUBLISHED: 07-29-2009
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Adult Japanese quail display left-eye/right-hemisphere dominance in visually guided sexual tracking. In 2 experiments, the authors set out to answer if this functional cerebral asymmetry is modifiable by posthatch monocular deprivation. In Experiment 1, the left or the right eye of 2-day old quail were closed for 70 days. Quail were run in a left- or a right-turning runway to obtain access to a conspecific of the opposite sex. The performance of both left and right eye systems was equal. In Experiment 2, the deprived eyes of the quail were opened and the previously open eyes were closed. They were tested with the same runways. Overall, running speed was very low, but the quail showed a left-eye/right-hemisphere superiority. Altogether, these experiments evince 3 insights into cerebral asymmetries in quail. First, posthatch asymmetries of visual input can alter lateralized behavior to an important extent. Second, cerebral asymmetries could involve an interhemispheric inhibition that can be modified by epigenetic factors. Third, even long-term visual deprivation does not abolish a previously established cerebral asymmetry.
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Learning of magnetic compass directions in pigeons.
Anim Cogn
PUBLISHED: 06-07-2009
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A proof of magnetic compass learning by pigeons under laboratory conditions has been attempted for decades, but all experiments have failed so far. The aim of the present study was to test whether pigeons can learn magnetic compass directions in an operant chamber if magnetic cues are presented as true spatial cues. Experimental sessions were carried out in the local geomagnetic field and in magnetic fields with matched total intensity and inclination, but different directions generated with Helmholtz-coils. Birds demonstrated successful learning with a performance level comparable to that in learning studies with magnetic anomalies. In addition, we compared the data from magnetic learning in the laboratory with performance from homing experiments in the field. The birds that were more successful in the learning experiment had vanishing bearings farther away from the home direction than the group mean at unfamiliar, but not at familiar sites. This might suggest that better learners explore unknown locations in a different way. Our findings represent the first evidence for operant magnetic compass learning in pigeons and also provide a link between behavioural data from the field and the laboratory.
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Vision during head bobbing: are pigeons capable of shape discrimination during the thrust phase?
Exp Brain Res
PUBLISHED: 05-29-2009
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Many birds show a characteristic forward and backward head movement, while walking, running and sometimes during landing flight, called head bobbing. During the hold phase, the head of the bird remains stable in space, while during the thrust phase, the head is rapidly moved forward. Three main functions for head bobbing have been proposed: Head bobbing might have a biomechanical cause, it might serve depth perception via motion parallax, or it might be an optokinetic response that primarily serves image stabilization for improved vision during the hold phase. To investigate vision during the different phases and in particular to test for visual suppression during the saccadic thrust phase, we tested pigeons on a shape discrimination task, presenting the stimuli exclusively either in the hold phase, thrust phase or at random times. Results clearly demonstrate that shape discrimination is as good during the thrust phase as it is during the hold phase.
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Pigeons identify individual humans but show no sign of recognizing them in photographs.
Behav. Processes
PUBLISHED: 05-25-2009
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Photographs, especially of humans, are widely used as stimuli in behavioural research with pigeons. Despite their abundant use, it is not clear to what extent pigeons perceive photographs as representing three-dimensional objects. To address this question, we trained 16 pigeons to identify individual, real-life humans. This discrimination depended primarily on visual cues from the heads of the persons. Subsequently, the pigeons were shown photographs of these individuals to test for transfer to a two-dimensional representation. Successful identification of a three-dimensional person did not facilitate learning of the corresponding photographs. These results demonstrate limitations of cross-recognition of complex objects and their photographs in pigeons.
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Ascending and descending mechanisms of visual lateralization in pigeons.
Philos. Trans. R. Soc. Lond., B, Biol. Sci.
PUBLISHED: 05-21-2009
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Brain asymmetries are a widespread phenomenon among vertebrates and show a common behavioural pattern. The right hemisphere mediates more emotional and instinctive reactions, while the left hemisphere deals with elaborated experience-based behaviours. In order to achieve a lateralized behaviour, each hemisphere needs different information and therefore different representations of the world. However, how these representations are accomplished within the brain is still unknown. Based on the pigeons visual system, we present experimental evidence that lateralized behaviour is the result of the interaction between the subtelencephalic ascending input directing more bilateral visual information towards the left hemisphere and the asymmetrically organized descending telencephalic influence on the tecto-tectal balance. Both the bilateral representation and the forebrain-modulated information processing might explain the left hemispheric dominance for complex learning and discrimination tasks.
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Head-turning asymmetries during kissing and their association with lateral preference.
Laterality
PUBLISHED: 04-25-2009
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A head-turning bias to the right side is one of the earliest functional asymmetries in human development and is already present during the final weeks of gestation. To test whether head-turning preference is related to other lateral preferences in adults, kissing behaviour of participants towards a symmetrical doll was observed to assess their spontaneous head-turning preference. Additionally, participants individual handedness, footedness, and eye preference were determined using questionnaires. A significant difference in handedness and footedness, but not eye preference, was found between left- and right-kissers, with right-kissers showing a stronger right-sided bias than left-kissers. These results support the assumption that the head-turning bias in humans may be able to induce or enhance other asymmetries of perception and action.
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Dichotic listening revisited: trial-by-trial ERP analyses reveal intra- and interhemispheric differences.
Neuropsychologia
PUBLISHED: 04-14-2009
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The dichotic listening (DL) paradigm is often used to assess brain asymmetries at the behavioral level. The aim of this study was to evaluate the dynamic temporal and topographical characteristics of event related potentials (ERPs) obtained with diotic and dichotic consonant-vowel (CV) stimuli from the same subjects. We used a novel approach in which we concurrently analyzed on a trial-by-trial basis ERP parameters during trials that resulted in a right ear advantage (REA) or left ear advantage (LEA) or that were presented under diotic (homonymous) conditions. CV syllables were used as auditory stimuli (/ba/, /da/, /ga/, /ka/, /pa/, /ta/). The EEG measurements were performed with 64 channels by mainly focusing on the N1P2, N2P3 and late negativity (LN) components. Overall, behavioral data revealed a clear REA. The central area showed higher amplitudes than the other locations for N1P2 responses. Additionally, responses were faster for the diotic, compared to the dichotic conditions. The LN had shorter latencies in trials resulting in a REA, compared with those producing a LEA. This result makes it likely that the overall REA is a time-bound effect, which can be explained by the structural theory of Kimura. Furthermore, the results demonstrated a specific spatiotemporal shift from central to frontal areas between N1P2 and LN that was pronounced in dichotic trials. This shift points towards the involvement of frontal areas in resolving conflicting input.
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Sex differences and the impact of steroid hormones on the developing human brain.
Cereb. Cortex
PUBLISHED: 04-11-2009
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Little is known about the hormonal effects of puberty on the anatomy of the developing human brain. In a voxel-based morphometry study, sex-related differences in gray matter (GM) volume were examined in 46 subjects aged 8-15 years. Males had larger GM volumes in the left amygdala, whereas females had larger right striatal and bilateral hippocampal GM volumes than males. Sexually dimorphic areas were related to Tanner stages (TS) of pubertal development and to circulating level of steroid hormones in a subsample of 30 subjects. Regardless of sex, amygdala and hippocampal volumes varied as a function of TS and were associated with circulating testosterone (TEST) levels. By contrast, striatal GM volumes were unrelated to pubertal development and circulating steroid hormones. Whole-brain regression analyses revealed positive associations between circulating estrogen levels and parahippocampal GM volumes as well as between TEST levels and diencephalic brain structures. In addition, a negative association was found between circulating TEST and left parietal GM volumes. These data suggest that GM development in certain brain regions is associated with sexual maturation and that pubertal hormones might have organizational effects on the developing human brain.
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Neuronal encoding of meaning: establishing category-selective response patterns in the avian prefrontal cortex.
Behav. Brain Res.
PUBLISHED: 03-31-2009
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Forebrain association areas interweave perceived stimuli with acquired representations of own actions and their outcome. Often, relevant stimuli come in a bewildering variety of shapes and sizes and we slowly have to learn to group them into meaningful categories. Therefore, the aim of the present study was twofold: First, to reveal how single units in the pigeons nidopallium caudolaterale (NCL), a functional analogue of the mammalian prefrontal cortex (PFC), encode stimuli that differ in visual features but not in behavioral relevance. The second aim was to understand how these categorical representations are established during learning. Recordings were made from NCL neurons while pigeons performed a go-nogo categorization paradigm. Responses during presentation of the two S+ stimuli and non-responding during presentation of the two S- stimuli were followed by reward. We recorded from two pigeons at different learning stages. In the beginning of the learning process, neurons were active during and shortly before reward, but only in go trials. These data suggest that during the early phase of learning avian prefrontal neurons code for rewards associated with the same behavioral demand, while ignoring feature differences of stimuli within one category. When learning progressed, (1) category selectivity became stronger, (2) responses selective for nogo stimuli appeared, and (3) reward-related responses disappeared in favor of category-selective responses during the stimulus phase. This backward shift in time resembles response patterns assumed by the temporal difference (TD) model of reinforcement learning, but goes beyond it, since it reflects the neuronal correlate of functional categories.
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Theory meets pigeons: the influence of reward-magnitude on discrimination-learning.
Behav. Brain Res.
PUBLISHED: 03-31-2009
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Modern theoretical accounts on reward-based learning are commonly based on reinforcement learning algorithms. Most noted in this context is the temporal-difference (TD) algorithm in which the difference between predicted and obtained reward, the prediction-error, serves as a learning signal. Consequently, larger rewards cause bigger prediction-errors and lead to faster learning than smaller rewards. Therefore, if animals employ a neural implementation of TD learning, reward-magnitude should affect learning in animals accordingly. Here we test this prediction by training pigeons on a simple color-discrimination task with two pairs of colors. In each pair, correct discrimination is rewarded; in pair one with a large-reward, in pair two with a small-reward. Pigeons acquired the large-reward discrimination faster than the small-reward discrimination. Animal behavior and an implementation of the TD-algorithm yielded comparable results with respect to the difference between learning curves in the large-reward and in the small-reward conditions. We conclude that the influence of reward-magnitude on the acquisition of a simple discrimination paradigm is accurately reflected by a TD implementation of reinforcement learning.
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When one hemisphere takes control: metacontrol in pigeons (Columba livia).
PLoS ONE
PUBLISHED: 02-19-2009
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Vertebrate brains are composed of two hemispheres that receive input, compute, and interact to form a unified response. How the partially different processes of both hemispheres are integrated to create a single output is largely unknown. In some cases one hemisphere takes charge of the response selection--a process known as metacontrol. Thus far, this phenomenon has only been shown in a handful of studies with primates, mostly conducted in humans. Metacontrol, however, is even more relevant for animals like birds with laterally placed eyes and complete chiasmatic decussation since visual input to the hemispheres is largely different.
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Peck tracking: a method for localizing critical features within complex pictures for pigeons.
Anim Cogn
PUBLISHED: 01-29-2009
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The pigeon is a standard animal in comparative psychology and is frequently used to investigate visuocognitive functions. Nonetheless, the strategies that pigeons use to discriminate complex visual stimuli remain a difficult area of study. In search of a reliable method to identify features that control the discrimination behaviour, pecking location was tracked using touch screen technology in a people-absent/people-present discrimination task. The correct stimuli contained human figures anywhere on the picture, but the birds were not required to peck on that part. However, the stimuli were designed in a way that only the human figures contained distinguishing information. All pigeons focused their pecks on a subarea of the distinctive human figures, namely the heads. Removal of the heads significantly impaired performance, while removal of other distinctive parts did not. Thus, peck tracking reveals the location within a complex visual stimulus that controls discrimination behaviour, and might be a valuable tool to reveal the strategies pigeons apply in visual discrimination tasks.
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Natural split-brain? Lateralized memory for task contingencies in pigeons.
Neurosci. Lett.
PUBLISHED: 01-27-2009
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The motion aftereffect (MAE) is an illusory motion in the opposite direction after the sudden halt of a prolonged visual moving stimulus. Birds could perceive the MAE as humans and other mammals. The present study was to investigate whether hemispheric asymmetries of visual processes affect this illusion. To this end, pigeons were trained to discriminate grating patterns which moved up, or down or stood still. The transfer tests were conducted under the binocular or monocular viewing condition. The choice behaviors of pigeons under the binocular and right-eye viewing condition (left hemisphere) were highly indicative for the perception of a MAE. However, the animals under the left-eye viewing condition (right hemisphere) did not change their choice patterns according to the different task displayed on the central stimulus key, but always stuck to the default option of pecking the response key ipsilateral to the open eye. We assume that memory for task contingencies were confined to the left hemisphere and could not be reached by the right half brain due to the absence of the corpus callosum.
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Dual coding of visual asymmetries in the pigeon brain: the interaction of bottom-up and top-down systems.
Exp Brain Res
PUBLISHED: 01-02-2009
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The pigeons visual system is an excellent model to investigate the ontogenetic and the neuronal foundations of cerebral asymmetries. Before hatching, lateralized visual stimulation induces structural asymmetries within the tectofugal pathway during a critical time window. Interhemispheric control mechanisms emerge presumably after hatching and stabilize these induced asymmetries. Once established, visual asymmetry in pigeons displays a left hemispheric dominance for complex learning and discrimination tasks and unravels how the interplay between bottom-up and top-down mechanisms generate a lateralized, hemispheric-specific visual analysis. The ascending visual (tectofugal) pathway displays cell size asymmetries and directs more bilateral visual information towards the left hemisphere. This bottom- up system is controlled by telencephalic top-down projections, which affect intra- and/or interhemispheric inhibitory systems in a presumably lateralized manner. Such a flexible organization allows the control of information transfer depending on the visual input and hence adapt the dominant processing mode to environmental requirements.
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Identification of two forebrain structures that mediate execution of memorized sequences in the pigeon.
J. Neurophysiol.
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The execution of action sequences is the basis of most behavior. However, little is known about the neural foundation of visuomotor sequence execution in birds, although pigeons are a classic model animal to study sequence learning and production. Recently, we identified two structures in the pigeon brain, the nidopallium intermedium medialis pars laterale (NIML) and the nidopallium caudolaterale (NCL), that are involved in the execution of a serial reaction time task (SRTT). In the SRTT sequence execution is always cue guided. Thus the previous study could not unambiguously clarify whether NCL and NIML contribute to a memory-based execution of sequential behavior. In addition, a possibly differential role of these two structures could not be identified. Therefore, the present study was conducted to further elucidate the role of NCL and NIML in sequence execution in a task where pigeons performed a memorized four-item sequence. Transient inactivation of each NIML and NCL severely impaired sequence execution. The results confirm and extend our previous findings. NIML and NCL seem to store sequence information in parallel. However, the results support the hypothesis that NCL, in contrast to NIML, is especially required for sequence initiation.
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Limb preferences in non-human vertebrates.
Laterality
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There is considerable debate about whether population-level asymmetries in limb preferences are uniquely human or are a common feature among vertebrates. In the present article the results of studies investigating limb preferences in all non-extinct vertebrate orders are systematically analysed by employing cladographic comparisons. These studies analysed 119 different species, with 61 (51.26%) showing evidence for population-level asymmetries, 20 (16.81%) showing evidence for individual-level asymmetries and 38 (31.93%) showing no evidence for asymmetry. The cladographic comparison revealed that research in several key taxa in particular (e.g., Chondrichtyes, Crocodylia, Atlantogenata and Palaeognathae) would have important implications for our understanding of the evolution of vertebrate limb preferences. Furthermore, the findings of the present study support the position that population-level asymmetries in limb preferences as such represent a common vertebrate feature. Looking into the details, however, some important differences from human handedness become visible: Non-human limb preferences typically show a less-skewed lateralisation pattern and there are larger numbers of individuals without a preference in most species compared to humans. Moreover, limb preferences in non-human animals are often less task-invariant than human handedness and are more frequently modulated by external factors and individual characteristics.
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Evidence for a Numerosity Category that is Based on Abstract Qualities of "Few" vs. "Many" in the Bottlenose Dolphin (Tursiops truncatus).
Front Psychol
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A previous study (Kilian et al., 2003) had demonstrated that bottlenose dolphins can discriminate visual stimuli differing in numerosity. The aim of the present study was twofold: first, we sought to determine if dolphins are able to use a numerical category based on "few" vs. "many" when discriminating stimuli according to the number of their constituent patterns. Second, we aimed to extend the previously demonstrated range of numbers, thereby testing the limits of the numerical abilities of bottlenose dolphins. To this end, one adult bottlenose dolphin learned to discriminate between two simultaneously presented stimuli which varied in the number of elements they contained. After initial training, several confounding parameters were excluded to render it likely that discrimination performance indeed depended on numerosity. Subsequently, the animal was tested with new stimuli of intermediate as well as higher numbers of elements. Once discrimination had been achieved, a reversal-training on a subset of stimuli was initiated. Afterward, the subject generalized the reversal successful to new and unreinforced stimuli. Our results reveal two main findings: firstly, our data strongly suggest a magnitude and a distance effect. Thus, coding of numerical information in dolphins might follow logarithmic scaling as postulated by the Weber-Fechner law. Secondly, after learning a reversal of contingencies, the dolphin generalized the reversal successful to new and unreinforced stimuli. Thus, within the limits of a study that was conducted with a single individual, our results suggest that dolphins are able to learn and use a numerical category that is based on abstract qualities of "few" vs. "many."
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Oxytocin modulates social distance between males and females.
J. Neurosci.
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In humans, interpersonal romantic attraction and the subsequent development of monogamous pair-bonds is substantially predicted by influential impressions formed during first encounters. The prosocial neuropeptide oxytocin (OXT) has been identified as a key facilitator of both interpersonal attraction and the formation of parental attachment. However, whether OXT contributes to the maintenance of monogamous bonds after they have been formed is unclear. In this randomized placebo-controlled trial, we provide the first behavioral evidence that the intranasal administration of OXT stimulates men in a monogamous relationship, but not single ones, to keep a much greater distance (~10-15 cm) between themselves and an attractive woman during a first encounter. This avoidance of close personal proximity occurred in the physical presence of female but not male experimenters and was independent of gaze direction and whether the female experimenter or the subject was moving. We further confirmed this unexpected finding using a photograph-based approach/avoidance task that showed again that OXT only stimulated men in a monogamous relationship to approach pictures of attractive women more slowly. Importantly, these changes cannot be attributed to OXT altering the attitude of monogamous men toward attractive women or their judgments of and arousal by pictures of them. Together, our results suggest that where OXT release is stimulated during a monogamous relationship, it may additionally promote its maintenance by making men avoid signaling romantic interest to other women through close-approach behavior during social encounters. In this way, OXT may help to promote fidelity within monogamous human relationships.
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Functional MRI and functional connectivity of the visual system of awake pigeons.
Behav. Brain Res.
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At present, functional MRI (fMRI) is increasingly used in animal research but the disadvantage is that the majority of the imaging is applied in anaesthetized animals. Only a few articles present results obtained in awake rodents. In this study both traditional fMRI and resting state (rsfMRI) were applied to four pigeons, that were trained to remain still while being imaged, removing the need for anesthesia. This is the first time functional connectivity measurements are performed in a non-mammalian species. Since the visual system of pigeons is a well-known model for brain asymmetry, the focus of the study was on the neural substrate of the visual system. For fMRI a visual stimulus was used and functional connectivity measurements were done with the entopallium (E; analog for the primary visual cortex) as a seed region. Interestingly in awake pigeons the left E was significantly functionally connected to the right E. Moreover we compared connectivity maps for a seed region in both hemispheres resulting in a stronger bilateral connectivity starting from left E then from right E. These results could be used as a starting point for further imaging studies in awake birds and also provide a new window into the analysis of hemispheric dominance in the pigeon.
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What is Visualize?

JoVE Visualize is a tool created to match the last 5 years of PubMed publications to methods in JoVE's video library.

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We use abstracts found on PubMed and match them to JoVE videos to create a list of 10 to 30 related methods videos.

Video X seems to be unrelated to Abstract Y...

In developing our video relationships, we compare around 5 million PubMed articles to our library of over 4,500 methods videos. In some cases the language used in the PubMed abstracts makes matching that content to a JoVE video difficult. In other cases, there happens not to be any content in our video library that is relevant to the topic of a given abstract. In these cases, our algorithms are trying their best to display videos with relevant content, which can sometimes result in matched videos with only a slight relation.