In JoVE (1)

Other Publications (55)

Articles by Paul Burgess in JoVE

 JoVE Behavior

Using Fiberless, Wearable fNIRS to Monitor Brain Activity in Real-world Cognitive Tasks

1Department of Medical Physics and Biomedical Engineering, Malet Place Engineering Building, University College London, 2Infrared Imaging Lab, Institute for Advanced Biomedical Technology (ITAB), Department of Neuroscience, Imaging and Clinical Sciences, University of Chieti-Pescara, 3Institute of Cognitive Neuroscience, Alexandra House, University College London

JoVE 53336

Other articles by Paul Burgess on PubMed

The Selective Impairment of Arithmetical Procedures

Cortex; a Journal Devoted to the Study of the Nervous System and Behavior. Sep, 2002  |  Pubmed ID: 12465669

The theoretical distinction between arithmetic facts and procedures was first made by Groen and Parkman (1972). This was confirmed with a neuropsychological single case described by Warrington (1982) who had impaired arithmetical facts but well preserved arithmetical procedures. Since this time there have been several patients described who showed a selective impairment of arithmetic facts. There have also been reports of cases with impaired arithmetical procedures. However, there has not yet been a case reported with the selective impairment of procedures in the context of intact arithmetic facts. This paper describes a patient, SR, with probable Alzheimer's dementia who had well preserved addition, multiplication and subtraction facts but who nevertheless had severe difficulties with a range of arithmetical procedures such as multidigit sums, decimals and fractions. The implications of this case for current theoretical models are discussed.

Ecological Validity of a Simplified Version of the Multiple Errands Shopping Test

Journal of the International Neuropsychological Society : JINS. Jan, 2003  |  Pubmed ID: 12570356

Shallice and Burgess (1991) reported the utility of the Multiple Errands Test (MET) in discriminating executive deficits in three frontal lobe patients with preserved high IQ, who were otherwise unimpaired on tests of executive function. The aim of this study was to ascertain the value of a simplified version of the MET (MET-SV) for use with the range of people more routinely encountered in clinical practice. Main findings were as follows: 1) The test discriminated well between neurological patients and controls, and the group effects remained when the difference in current general cognitive functions (WAIS-R FSIQ) was taken into account. 2) The best predictors of performance in the healthy control group (n = 46) were age and the number of times participants asked for help (with more requests associated with poorer performance). 3) In the neurological group, two clear patterns of failure emerged, with performance either characterized by rule breaking or failure to achieve tasks. These two patterns were associated with different dysexecutive symptoms in everyday life. 4) The patients not only made more errors than controls, but also different ones. A scoring method that took this into account markedly increased test sensitivity. 5) Many patients passed traditional tests of executive frontal lobe function but still failed the MET-SV. This pattern was strongly associated with observed dysexecutive symptoms in everyday life. The results demonstrate the clinical utility of the test, and suggest that there are two common and independent sources of failure on multitasking tests in a general neurological population: memory dysfunction, and initiation problems.

The Role of the Rostral Frontal Cortex (area 10) in Prospective Memory: a Lateral Versus Medial Dissociation

Neuropsychologia. 2003  |  Pubmed ID: 12667527

Using the H(2)(15)O PET method, we investigated whether previous findings of regional cerebral blood flow (rCBF) changes in the polar and superior rostral aspects of the frontal lobes (principally Brodmann's area (BA) 10) during prospective memory (PM) paradigms (i.e. those involving carrying out an intended action after a delay) can be attributed merely to the greater difficulty of such tasks over the baseline conditions typically employed. Three different tasks were administered under four conditions: baseline simple RT; attention-demanding ongoing task only; ongoing task plus a delayed intention (unpracticed); ongoing task plus delayed intention (practiced). Under prospective memory conditions, we found significant rCBF decreases in the superior medial aspects of the rostral prefrontal cortex (BA 10) relative to the baseline or ongoing task only conditions. However more lateral aspects of area 10 (plus the medio-dorsal thalamus) showed the opposite pattern, with rCBF increases in the prospective memory conditions relative to the other conditions. These patterns were broadly replicated over all three tasks. Since both the medial and lateral rostral regions showed: (a) instances where rCBF was lower during a more effortful condition (as estimated by increased RTs and error rates) than in a less effortful one; and (b) there was no correlation between rCBF and RT durations or number of errors in these regions, a simple task difficulty explanation of the rCBF changes in the rostral aspects of the frontal lobes during prospective memory tasks is rejected. Instead, the favoured explanation concentrates upon the particular processing demands made by these situations irrespective of the precise stimuli used or the exact nature of the intention. Moreover, the results suggest different roles for medial and lateral rostral prefrontal cortex, with the former involved in suppressing internally-generated thought, and the latter in maintaining it.

Distinct Roles for Lateral and Medial Anterior Prefrontal Cortex in Contextual Recollection

Journal of Neurophysiology. Jul, 2005  |  Pubmed ID: 15728761

A key feature of human recollection is the ability to remember details of the context in which events were experienced, as well as details of the events themselves. Previous studies have implicated a number of regions of prefrontal cortex in contextual recollection, but the role of anterior prefrontal cortex has so far resisted detailed characterization. We used event-related functional MRI (fMRI) to contrast recollection of two forms of contextual information: 1) decisions one had previously made about stimuli (task memory) and 2) which of two temporally distinct lists those stimuli had been presented in (list memory). In addition, a retrieval cue manipulation permitted evaluation of the stage of the retrieval process in which the activated regions might be involved. The results indicated that anterior prefrontal cortex responded significantly more during recollection of task than list context details. Furthermore, activation profiles for lateral and medial aspects of anterior prefrontal cortex suggested differing roles in recollection. Lateral regions seem to be more involved in the early retrieval specification stages of recollection, with medial regions contributing to later stages (e.g., monitoring and verification).

Involvement of Rostral Prefrontal Cortex in Selection Between Stimulus-oriented and Stimulus-independent Thought

The European Journal of Neuroscience. Mar, 2005  |  Pubmed ID: 15813952

We used functional magnetic resonance imaging to investigate brain activity while healthy subjects performed three different tasks, each of which alternated between: (i) phases relying on stimulus-oriented thought (i.e. cognitive processes provoked by incoming sensory information); and (ii) phases relying on stimulus-independent thought (i.e. cognitive processes that were not related to any information in the immediate sensory environment). Within each task, the two phases were matched as closely as possible. In all three tasks, lateral rostral prefrontal cortex was transiently activated by a switch between stimulus-oriented and stimulus-independent thought (regardless of the direction of the switch). Medial rostral prefrontal cortex consistently exhibited sustained activity for stimulus-oriented vs. stimulus-independent thought. These results suggest the involvement of rostral prefrontal cortex in selection between stimulus-oriented and stimulus-independent cognitive processes.

An Unusual Skin Metastasis: Esophageal Squamous Cell Carcinoma Metastasizing to the Nose Following Nasogastric Tube Suture

Plastic and Reconstructive Surgery. Aug, 2005  |  Pubmed ID: 16079730

Anterior Prefrontal Cortex and the Recollection of Contextual Information

Neuropsychologia. 2005  |  Pubmed ID: 16154453

Recollective memory can involve the retrieval of many different kinds of contextual information, including where and when an event took place, as well as our thoughts and feelings at the time. The brain regions associated with this ability were examined in an event-related fMRI experiment, where participants made decisions about words or famous faces which were presented either on the left or right of a monitor screen. Subsequently, the studied words and faces were again presented and participants underwent fMRI brain scanning while recollecting either which of the decisions they had made on each item ("task memory"), or whether it had been presented on the left or right of the screen ("position memory"). A functional dissociation was observed within anterior prefrontal cortex (principally Brodmann's area 10), with activation in lateral regions associated with remembering either type of information (relative to baseline), and a medial anterior PFC region showing significantly greater activation during the "task memory" conditions. These results suggest different roles for lateral and medial anterior prefrontal cortex in recollection.

Catastrophe Loss Modelling of Storm-surge Flood Risk in Eastern England

Philosophical Transactions. Series A, Mathematical, Physical, and Engineering Sciences. Jun, 2005  |  Pubmed ID: 16191657

Probabilistic catastrophe loss modelling techniques, comprising a large stochastic set of potential storm-surge flood events, each assigned an annual rate of occurrence, have been employed for quantifying risk in the coastal flood plain of eastern England. Based on the tracks of the causative extratropical cyclones, historical storm-surge events are categorized into three classes, with distinct windfields and surge geographies. Extreme combinations of "tide with surge" are then generated for an extreme value distribution developed for each class. Fragility curves are used to determine the probability and magnitude of breaching relative to water levels and wave action for each section of sea defence. Based on the time-history of water levels in the surge, and the simulated configuration of breaching, flow is time-stepped through the defences and propagated into the flood plain using a 50 m horizontal-resolution digital elevation model. Based on the values and locations of the building stock in the flood plain, losses are calculated using vulnerability functions linking flood depth and flood velocity to measures of property loss. The outputs from this model for a UK insurance industry portfolio include "loss exceedence probabilities" as well as "average annualized losses", which can be employed for calculating coastal flood risk premiums in each postcode.

Differential Functions of Lateral and Medial Rostral Prefrontal Cortex (area 10) Revealed by Brain-behavior Associations

Cerebral Cortex (New York, N.Y. : 1991). Dec, 2006  |  Pubmed ID: 16421331

We analyzed the behavioral data from 104 neuroimaging studies using positron emission tomography or functional magnetic resonance imaging that reported activation peaks in rostral prefrontal cortex (PFC), approximating Brodmann's area 10. The distribution of absolute x coordinates of activation peaks (i.e., x coordinate regardless of hemisphere) differed significantly from a unimodal normal distribution, reflecting distinct clusters of activation in lateral and medial subregions. These 2 clusters were associated with different patterns of behavioral data. Lateral activations were associated with contrasts between experimental and control conditions where response times (RTs) were slower in the experimental condition. Medial activations were associated with contrasts where RTs were, if anything, faster in experimental than control conditions. These findings place important constraints on theories of rostral PFC functions.

Performance-related Activity in Medial Rostral Prefrontal Cortex (area 10) During Low-demand Tasks

Journal of Experimental Psychology. Human Perception and Performance. Feb, 2006  |  Pubmed ID: 16478325

Neuroimaging studies have frequently observed relatively high activity in medial rostral prefrontal cortex (PFC) during rest or baseline conditions. Some accounts have attributed this high activity to the occurrence of unconstrained stimulus-independent and task-unrelated thought processes during baseline conditions. Here, the authors investigated the alternative possibility that medial rostral PFC supports attention toward the external environment during low-demand conditions. Participants performed a baseline simple reaction time (RT) task, along with 3 other tasks that differed in the requirement to attend to external stimuli versus stimulus-independent thought. Medial rostral PFC activation was observed in the baseline task and in a condition requiring strong engagement with external stimuli, relative to 2 conditions with a greater requirement for stimulus-independent thought. An important finding was that activity in this region was associated with faster RTs in the baseline task, ruling out an explanation in terms of task-unrelated thought processes during this condition. Thus, at least under certain circumstances, medial rostral PFC appears to support attention toward the external environment, facilitating performance in situations that do not require extensive processing of experimental stimuli.

Differential Components of Prospective Memory? Evidence from FMRI

Neuropsychologia. 2006  |  Pubmed ID: 16513147

Two of the principal components of prospective memory (i.e., remembering to carry out delayed intentions) are recognizing the appropriate context to act ("cue identification") and remembering the action to be performed ("intention retrieval"). In this experiment, the demands on these components were manipulated while measuring brain activity using fMRI to explore whether the two components share a common neural basis. The results showed significant behavioral differences between the cue identification and intention retrieval conditions. However, a consistent pattern of hemodynamic changes was found in both prospective memory conditions in anterior prefrontal cortex (BA 10), with lateral BA 10 activation accompanied by medial BA 10 deactivation. These effects were more pronounced when demands on intention retrieval were high. This is consistent with the hypothesis that anterior prefrontal cortex (area 10) supports the biasing of attention between external events (e.g., identifying the cue amid distracting stimuli) and internal thought processes (i.e., maintaining the intention and remembering the intended actions). Together, the results suggest that whilst cue identification and intention retrieval may be behaviorally separable, they share at least some common neural basis in anterior prefrontal cortex.

The Case for the Development and Use of "ecologically Valid" Measures of Executive Function in Experimental and Clinical Neuropsychology

Journal of the International Neuropsychological Society : JINS. Mar, 2006  |  Pubmed ID: 16573854

This article considers the scientific process whereby new and better clinical tests of executive function might be developed, and what form they might take. We argue that many of the traditional tests of executive function most commonly in use (e.g., the Wisconsin Card Sorting Test; Stroop) are adaptations of procedures that emerged almost coincidentally from conceptual and experimental frameworks far removed from those currently in favour, and that the prolongation of their use has been encouraged by a sustained period of concentration on "construct-driven" experimentation in neuropsychology. This resulted from the special theoretical demands made by the field of executive function, but was not a necessary consequence, and may not even have been a useful one. Whilst useful, these tests may not therefore be optimal for their purpose. We consider as an alternative approach a function-led development programme which in principle could yield tasks better suited to the concerns of the clinician because of the transparency afforded by increased "representativeness" and "generalisability." We further argue that the requirement of such a programme to represent the interaction between the individual and situational context might also provide useful constraints for purely experimental investigations. We provide an example of such a programme with reference to the Multiple Errands and Six Element tests.

Discriminating Imagined from Perceived Information Engages Brain Areas Implicated in Schizophrenia

NeuroImage. Aug, 2006  |  Pubmed ID: 16797186

Some of the symptoms of schizophrenia may reflect a difficulty discriminating between information that was perceived from the outside world and information that was imagined. This study used fMRI to examine the brain regions associated with this reality monitoring ability in healthy volunteers, who recollected whether information had previously been perceived or imagined, or whether information had been presented on the left or right of a monitor screen. Recent studies have suggested that schizophrenia may be associated particularly with dysfunction in medial anterior prefrontal cortex, thalamus, and cerebellum. In our data, activation in all three of these regions of interest was significantly greater during recollection of whether stimuli had been perceived or imagined versus recollection of stimulus position. In addition, reduced prefrontal activation was associated with the same misattribution error that has been observed in schizophrenia. These results indicate a possible link between the brain areas implicated in schizophrenia and the regions supporting the ability to discriminate between perceived and imagined information.

Functional Specialization Within Rostral Prefrontal Cortex (area 10): a Meta-analysis

Journal of Cognitive Neuroscience. Jun, 2006  |  Pubmed ID: 16839301

One of the least well understood regions of the human brain is rostral prefrontal cortex, approximating Brodmann's area 10. Here, we investigate the possibility that there are functional subdivisions within this region by conducting a meta-analysis of 104 functional neuroimaging studies (using positron emission tomography/functional magnetic resonance imaging). Studies involving working memory and episodic memory retrieval were disproportionately associated with lateral activations, whereas studies involving mentalizing (i.e., attending to one's own emotions and mental states or those of other agents) were disproportionately associated with medial activations. Functional variation was also observed along a rostral-caudal axis, with studies involving mentalizing yielding relatively caudal activations and studies involving multiple-task coordination yielding relatively rostral activations. A classification algorithm was trained to predict the task, given the coordinates of each activation peak. Performance was well above chance levels (74% for the three most common tasks; 45% across all eight tasks investigated) and generalized to data not included in the training set. These results point to considerable functional segregation within rostral prefrontal cortex.

Differential Involvement of Regions of Rostral Prefrontal Cortex (Brodmann Area 10) in Time- and Event-based Prospective Memory

International Journal of Psychophysiology : Official Journal of the International Organization of Psychophysiology. Jun, 2007  |  Pubmed ID: 17126435

Rostral prefrontal cortex (approximating Brodmann area 10) has been shown repeatedly to have a role in the maintenance and realization of delayed intentions that are triggered by event cues (i.e., event-based prospective memory). The cerebral organization of the processes associated with the use of time cues (time-based prospective memory) has however received less attention. In two positron emission tomography (PET) studies we therefore examined brain activity associated with time- and event-based prospective memory tasks. In the time-based condition of the first study, young healthy volunteers were asked to make a prospective response based on their self-estimation of the passage of time while engaged in an attention-demanding ongoing activity. In the time-based condition of the second study, participants had a clock available in the ongoing task display and did not need to estimate the time for the prospective response. In the event-based condition of both studies, participants were asked to make a prospective response when prospective cues were presented in ongoing trials. Both studies showed activation differences in rostral prefrontal cortex according to whether the task was time- or event-based. In study one, an area of left superior frontal gyrus was more active in the time-based condition. In study two, three rostral prefrontal regions were more active in the time-based condition: right superior frontal gyrus, anterior medial frontal lobe and anterior cingulate gyrus. A region in left superior frontal gyrus, different from the area found in the first study, was more active in the event-based condition. These results indicate involvement of multiple brain regions of rostral prefrontal cortex in time- and event-based prospective memory. The results are interpreted as reflecting the differing processing demands made by event- or time-based prospective memory tasks, and the differing demands of time-based tasks according to whether a clock is present as an aid.

Function and Localization Within Rostral Prefrontal Cortex (area 10)

Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences. May, 2007  |  Pubmed ID: 17403644

We propose that rostral prefrontal cortex (PFC; approximating area 10) supports a cognitive system that facilitates either stimulus-oriented (SO) or stimulus-independent (SI) attending. SO attending is the behaviour required to concentrate on current sensory input, whereas SI attending is the mental processing that accompanies self-generated or self-maintained thought. Regions of medial area 10 support processes related to the former, whilst areas of lateral area 10 support processes that enable the latter. Three lines of evidence for this 'gateway hypothesis' are presented. First, we demonstrate the predicted patterns of activation in area 10 during the performance of new tests designed to stress the hypothetical function. Second, we demonstrate area 10 activations during the performance of established functions (prospective memory, context memory), which should hypothetically involve the proposed attentional system. Third, we examine predictions about behaviour-activation patterns within rostral PFC that follow from the hypothesis. We show with meta-analysis of neuroimaging investigations that these predictions are supported across a wide variety of tasks, thus establishing a general principle for functional imaging studies of this large brain region. We then show that while the gateway hypothesis accommodates a large range of findings relating to the functional organization of area 10 along a medial-lateral dimension, there are further principles relating to other dimensions and functions. In particular, there is a functional dissociation between the anterior medial area 10, which supports processes required for SO attending, and the caudal medial area 10, which supports processes relating to mentalizing.

The Gateway Hypothesis of Rostral Prefrontal Cortex (area 10) Function

Trends in Cognitive Sciences. Jul, 2007  |  Pubmed ID: 17548231

Rostral prefrontal cortex (PFC) is a large brain region, and is unusually large in humans. Therefore, it seems likely that it might support functions that are central to cognition. However, until recently, almost nothing was known about what these functions might be. The 'gateway hypothesis' places these abilities at the centre of human mental processing. It maintains that rostral PFC supports mechanisms that enable us to attend, to a novel degree, either to environmental stimuli, or by contrast, to self-generated or maintained representations (i.e. the 'thoughts in our head'). In this way, investigations into the functions of rostral PFC will reveal key new insights into how human and non-human mental abilities differ.

Comment on "Wandering Minds: the Default Network and Stimulus-independent Thought"

Science (New York, N.Y.). Jul, 2007  |  Pubmed ID: 17615325

Mason et al. (Reports, 19 January 2007, p. 393) attributed activity in certain regions of the "resting" brain to the occurrence of mind-wandering. However, previous research has demonstrated the difficulty of distinguishing this type of stimulus-independent thought from stimulus-oriented thought (e.g., watchfulness). Consideration of both possibilities is required to resolve this ambiguity.

Distinct Regions of Medial Rostral Prefrontal Cortex Supporting Social and Nonsocial Functions

Social Cognitive and Affective Neuroscience. Sep, 2007  |  Pubmed ID: 18985143

While some recent neuroimaging studies have implicated medial rostral prefrontal cortex (MPFC) in 'mentalizing' and self-reflection, others have implicated this region in attention towards perceptual vs self-generated information. In order to reconcile these seemingly contradictory findings, we used fMRI to investigate MPFC activity related to these two functions in a factorial design. Participants performed two separate tasks, each of which alternated between 'stimulus-oriented phases' (SO), where participants attended to task-relevant perceptual information, and 'stimulus-independent phases' (SI), where participants performed the same tasks in the absence of such information. In half of the blocks ('mentalizing condition'), participants were instructed that they were performing these tasks in collaboration with an experimenter; in other blocks ('non-mentalizing condition'), participants were instructed that the experimenter was not involved. In fact, the tasks were identical in these conditions. Neuroimaging data revealed adjacent but clearly distinct regions of activation within MPFC related to (i) mentalizing vs non-mentalizing conditions (relatively caudal/superior) and (ii) SO vs SI attention (relatively rostral/inferior). These results generalized from one task to the other, suggesting a new axis of functional organization within MPFC.

Development of Rostral Prefrontal Cortex and Cognitive and Behavioural Disorders

Developmental Medicine and Child Neurology. Mar, 2008  |  Pubmed ID: 18190537

Information on the development and functions of rostral prefrontal cortex (PFC), or Brodmann area 10, has been gathered from different fields, from anatomical development to functional neuroimaging in adults, and put forward in relation to three particular cognitive and behavioural disorders. Rostral PFC is larger and has a lower cell density in humans than in other primates. It also has a large number of dendritic spines per cell and numerous connections to the supramodal cortex. These characteristics suggest that rostral PFC is likely to support processes of integration or coordination of inputs that are particularly developed in humans. The development of rostral PFC is prolonged, with decreases in grey matter and synaptic density continuing into adolescence. Functions attributed to rostral PFC, such as prospective memory, seem similarly to follow a prolonged development until adulthood. Neuroimaging studies have generally found a reduced recruitment of rostral PFC, for example in tasks requiring response inhibition, in adults compared with children or adolescents, which is consistent with maturation of grey matter. The examples of autism, attention-deficit-hyperactivity disorder, and schizophrenia show that rostral PFC could be affected in several disorders as a result of the susceptibility of its prolonged maturation to developmental abnormalities.

Executive Function

Current Biology : CB. Feb, 2008  |  Pubmed ID: 18269902

Distinct Roles for Lateral and Medial Rostral Prefrontal Cortex in Source Monitoring of Perceived and Imagined Events

Neuropsychologia. Apr, 2008  |  Pubmed ID: 18294660

Rostral prefrontal cortex (PFC) is known to be involved in source memory, the ability to recollect contextual information about an event. However it is unclear whether subregions of rostral PFC may be differentially engaged during the recollection of different kinds of source detail. We used event related functional MRI to contrast two forms of source recollection: (1) recollection of whether stimuli had previously been perceived or imagined, and (2) recollection of which of two temporally distinct lists those stimuli had been presented in. Lateral regions of rostral PFC were activated in both tasks. However medial regions of rostral PFC were activated only when participants were required to recollect source information for self-generated, "imagined" stimuli, indicating a specific role in self-referential processing. In addition, reduced activity in a region of medial ventro-caudal PFC/basal forebrain was associated with making "imagined-to-perceived" confabulation errors. These results suggest that whilst the processing resources supported by some regions of lateral rostral PFC play a general role in source recollection, those supported by medial rostral PFC structures may be more specialised in their contributions.

Atypical Recruitment of Medial Prefrontal Cortex in Autism Spectrum Disorders: an FMRI Study of Two Executive Function Tasks

Neuropsychologia. 2008  |  Pubmed ID: 18485420

Recent studies have suggested an uneven profile of executive dysfunction in autism spectrum disorders (ASD). For example, some authors have reported deficits on newly developed tests of executive function sensitive to rostral prefrontal function, despite spared, or even superior, performance on other tests. We investigated the performance of a group of high-functioning participants with ASD (N=15) and an age- and IQ-matched control group (N=18) on two executive function tests, whilst undergoing functional magnetic resonance imaging (fMRI). Behaviourally, there were no significant differences between the two groups. In a classical test of executive function (random response generation), BOLD signal differed between the groups in the cerebellum but not in the frontal lobes. However, on a new test of executive function (selection between stimulus-oriented and stimulus-independent thought), the ASD group exhibited significantly greater signal-change in medial rostral prefrontal cortex (especially Brodmann Area 10) in the comparison of stimulus-oriented versus stimulus-independent attention. In addition, the new test (but not the classical test) provided evidence for abnormal functional organisation of medial prefrontal cortex in ASD. These results underline the heterogeneity of different tests of executive function, and suggest that executive functioning in ASD is associated with task-specific functional change.

Beyond the Mainstream - Health Gains in Remote Aboriginal Communities

Australian Family Physician. Dec, 2008  |  Pubmed ID: 19142270

Aboriginal and Torres Strait Islander Australians have long asserted the health benefits of maintaining close links with the lands and seas to which they have ancestral connections.

Abnormal Functional Specialization Within Medial Prefrontal Cortex in High-functioning Autism: a Multi-voxel Similarity Analysis

Brain : a Journal of Neurology. Apr, 2009  |  Pubmed ID: 19174370

Multi-voxel pattern analyses have proved successful in 'decoding' mental states from fMRI data, but have not been used to examine brain differences associated with atypical populations. We investigated a group of 16 (14 males) high-functioning participants with autism spectrum disorder (ASD) and 16 non-autistic control participants (12 males) performing two tasks (spatial/verbal) previously shown to activate medial rostral prefrontal cortex (mrPFC). Each task manipulated: (i) attention towards perceptual versus self-generated information and (ii) reflection on another person's mental state ('mentalizing'versus 'non-mentalizing') in a 2 x 2 design. Behavioral performance and group-level fMRI results were similar between groups. However, multi-voxel similarity analyses revealed strong differences. In control participants, the spatial distribution of activity generalized significantly between task contexts (spatial/verbal) when examining the same function (attention/mentalizing) but not when comparing different functions. This pattern was disrupted in the ASD group, indicating abnormal functional specialization within mrPFC, and demonstrating the applicability of multi-voxel pattern analysis to investigations of atypical populations.

Differential Relationship of Frontal Pole and Whole Brain Volumetric Measures with Age in Neuroleptic-naïve Schizophrenia and Healthy Subjects

Schizophrenia Research. Apr, 2009  |  Pubmed ID: 19185466

Brodmann's area (BA) 10, which occupies the frontal pole (FP) of the human brain, has been proven to play a central role in the executive control of cognitive operations. Previous in vivo morphometric studies of the FP have been limited by the lack of an accepted boundary of its posterior limit. We studied the FP gray matter volume in 23 healthy subjects who were age-, sex-, and education-matched to 23 neuroleptic-naïve recent-onset schizophrenia subjects in the age span 20-40 years, using a cytoarchitectonically and functionally valid landmark-based definition of its posterior boundary that we proposed recently (John, J.P., Yashavantha, B.S., Gado, M., Veena, R., Jain, S., Ravishankar, S., Csernansky, J.G., 2007. A proposal for MRI-based parcellation of the frontal pole. Brain Struct. Funct. 212, 245-253. 2007). Additionally, we examined the relationship between FP volume and age in both healthy and schizophrenia subjects to examine evidence for a possible differential relationship between these variables across the samples. A major finding of the study was the absence of a group-level difference in frontal pole gray volumes between the healthy and schizophrenia participants. However, a more complex finding emerged in relation to age effects. The healthy participants showed an inverse relationship of FP gray volume with age, even after taking total brain volume differences into account. But this age effect was completely absent in the schizophrenia group. Moreover, all the volumetric measures in schizophrenia subjects showed substantially higher range, variance, skewness and kurtosis when compared to those of healthy subjects. These findings have implications in understanding the possible role of FP in the pathophysiology of schizophrenia.

Impairments on "open-ended" Executive Function Tests in Autism

Autism Research : Official Journal of the International Society for Autism Research. Jun, 2009  |  Pubmed ID: 19536839

The executive function (EF) theory of autism has received much support recently from a growing number of studies. However, executive impairments have not always been easy to identify consistently and so novel "ecologically valid" tests have been designed which tap into real-life scenarios that are relevant to and representative of everyday behavior. One characteristic of many of these tasks is that they present the participant with an "ill-structured" or "open-ended" situation. Here, we investigated the possibility that tasks with greater degrees of open-endedness might prove more sensitive to detecting executive impairment in autism. Forty-five children with autism spectrum disorder (ASD) were compared to 27 age- and IQ-matched control children on a range of cognitive tests of EF. Group differences were found on half of the tasks, with the greatest degree of impairment detected on the more open-ended tasks. The ASD group also performed more poorly on a simple control condition of a task. Detailed consideration of task performance suggested that the ASD group tended to create fewer spontaneous strategies and exhibit more idiosyncratic behavior, which particularly disadvantaged them on the more open-ended tasks. These kinds of behaviors have been reported in studies of neurological patients with frontal lobe involvement, prima facie suggesting a link between the scientific fields. However, we suggest that this behavior might equally result from a poor understanding of the implicit demands made by the experimenter in open-ended test situations, due to the socio-communicative difficulties of these children.

Advantages of the Multiple Case Series Approach to the Study of Cognitive Deficits in Autism Spectrum Disorder

Neuropsychologia. Nov, 2009  |  Pubmed ID: 19580821

In the neuropsychological case series approach, tasks are administered that tap different cognitive domains, and differences within rather than across individuals are the basis for theorising; each individual is effectively their own control. This approach is a mainstay of cognitive neuropsychology, and is particularly suited to the study of populations with heterogeneous deficits. However it has very rarely been applied to the study of cognitive differences in autism spectrum disorder (ASD). Here, we investigate whether this approach can yield information beyond that given by the typical group study method, when applied to an ASD population. Twenty-one high-functioning adult ASD participants and 22 IQ, age, and gender-matched control participants were administered a large battery of neuropsychological tests that would represent a typical neuropsychological assessment for neurological patients in the United Kingdom. The data were analysed using both group and single-case study methods. The group analysis revealed a limited number of deficits, principally on tests with a large executive function component, with no impairment in more routine abilities such as basic attending, language and perception. Single-case study analysis proved more fruitful revealing evidence of considerable variation in abilities both between and within ASD participants. Both sub-normal and supra-normal performance were observed, with the most defining feature of the ASD group being this variability. We conclude that the use of group-level analysis alone in the study of cognitive deficits in ASD risks missing cognitive characteristics that may be vitally important both theoretically and clinically, and even may be misleading because of averaging artifact.

Separable Brain Systems Supporting Cued Versus Self-initiated Realization of Delayed Intentions

Journal of Experimental Psychology. Learning, Memory, and Cognition. Jul, 2009  |  Pubmed ID: 19586260

In everyday life, one can link anticipated specific cues (e.g. visiting a restaurant) with desired actions (e.g., ordering a healthy meal). Alternatively, intentions such as "I intend to eat more healthily" present the option to act when one encounters the same cue. In the first case, a specific cue triggers a specific action; in the second, one must act in a more self-initiated manner. The authors compared such scenarios using functional magnetic resonance imaging. Participants were either instructed to respond in a particular manner to target events (cued condition) or told that they would score points for such responses, without being told that they were necessary (self-initiated condition). Although conditions differed only in the wording of instructions, the self-initiated condition was associated with poorer performance and greater activity in a predominantly frontoparietal network. Responses to targets in the self-initiated and cued conditions yielded greater activity in lateral and medial Brodmann area 10, respectively. The authors suggest that these results reflect differing demands for self-initiated versus externally cued behavior following different types of instruction, in line with the distinction between goal intentions and implementation intentions proposed by P. M. Gollwitzer and colleagues.

Mesulam's Frontal Lobe Mystery Re-examined

Restorative Neurology and Neuroscience. 2009  |  Pubmed ID: 19847072

Mesulam's (1986) mystery is that some patients with frontal lobe damage may show no cognitive impairment according to traditional office-based assessment procedures, yet nevertheless show marked cognitive handicap in everyday life. Mesulam suggested that "the office setting may introduce sufficient external structure to suppress some of these behavioral tendencies" (p. 322). We ask if it is indeed the office setting that is the problem, or whether it is that traditional assessments do not measure the full range of cognitive functions supported by prefrontal cortex.

Further Development of the Multiple Errands Test: Standardized Scoring, Reliability, and Ecological Validity for the Baycrest Version

Archives of Physical Medicine and Rehabilitation. Nov, 2009  |  Pubmed ID: 19892074

(1) To determine the summary scores on the Baycrest Multiple Errands Test (BMET) that best discriminate between community dwelling people with traumatic brain injury or stroke and matched controls; (2) to determine interrater reliability; (3) to evaluate further the ecological validity.

When I Think About Me and Simulate You: Medial Rostral Prefrontal Cortex and Self-referential Processes

NeuroImage. Apr, 2010  |  Pubmed ID: 20045478

While neuroimaging studies implicate medial rostral prefrontal cortex (mrPFC) in self-referential processing, simulation accounts of social cognition suggest that this region also supports thinking about other people. This study tested the prediction that mrPFC might be involved in appraising the personality traits of another person to the degree that this person is perceived as similar to oneself. We also examined whether recruiting common processes for thinking about oneself and others might impact on subsequent memory for those judgments. Functional MRI was used while two factors were crossed: (i) the requirement to engage in personality trait or episodic source memory judgments and (ii) the reference for these judgments (i.e., oneself or a friend). The results link haemodynamic changes in mrPFC to both personality judgments about oneself and subsequent episodic memory retrieval of these judgments. The degree to which BOLD signal in this region was also associated with thinking about others correlated with perceived similarity in both tasks, thus corroborating simulation accounts. Moreover, participants who perceived themselves as having similar traits to their friends tended to be poorer at remembering whether they had made trait judgments in reference to themselves or their friend. This behavioral effect was reflected in the BOLD signal in mrPFC: there was a positive correlation between signal change for self versus friend judgments and subsequent memory for the reference of such judgments. The results suggest that investigations of mrPFC activity in the context of self/other judgments should take into account this psychological similarity effect.

Neural Correlates of Task and Source Switching: Similar or Different?

Biological Psychology. Mar, 2010  |  Pubmed ID: 20093165

Controlling everyday behaviour relies on the ability to configure appropriate task sets and guide attention towards information relevant to the current context and goals. Here, we ask whether these two aspects of cognitive control have different neural bases. Electrical brain activity was recorded while sixteen adults performed two discrimination tasks. The tasks were performed on either a visual input (letter on the screen) or self-generated information (letter generated internally by continuing the alphabetical sequence). In different blocks, volunteers either switched between (i) the two tasks, (ii) the two sources of information, or (iii) tasks and source of information. Event-related potentials differed significantly between switch and no-switch trials from an early point in time, encompassing at least three distinct effects. Crucially, although these effects showed quantitative differences across switch types, no qualitative differences were observed. Thus, at least under the current circumstances, switching between different tasks and between perceptually derived or self-generated sources of information rely on similar neural correlates until at least 900 ms after the onset of a switch event.

Specialization of the Rostral Prefrontal Cortex for Distinct Analogy Processes

Cerebral Cortex (New York, N.Y. : 1991). Nov, 2010  |  Pubmed ID: 20156841

Analogical reasoning is central to learning and abstract thinking. It involves using a more familiar situation (source) to make inferences about a less familiar situation (target). According to the predominant cognitive models, analogical reasoning includes 1) generation of structured mental representations and 2) mapping based on structural similarities between them. This study used functional magnetic resonance imaging to specify the role of rostral prefrontal cortex (PFC) in these distinct processes. An experimental paradigm was designed that enabled differentiation between these processes, by temporal separation of the presentation of the source and the target. Within rostral PFC, a lateral subregion was activated by analogy task both during study of the source (before the source could be compared with a target) and when the target appeared. This may suggest that this subregion supports fundamental analogy processes such as generating structured representations of stimuli but is not specific to one particular processing stage. By contrast, a dorsomedial subregion of rostral PFC showed an interaction between task (analogy vs. control) and period (more activated when the target appeared). We propose that this region is involved in comparison or mapping processes. These results add to the growing evidence for functional differentiation between rostral PFC subregions.

Recruitment of Lateral Rostral Prefrontal Cortex in Spontaneous and Task-related Thoughts

Quarterly Journal of Experimental Psychology (2006). Sep, 2010  |  Pubmed ID: 20221947

Behavioural and neuroimaging studies suggest that spontaneous and task-related thought processes share common cognitive mechanisms and neural bases. Lateral rostral prefrontal cortex (RPFC) is a brain region that has been implicated both in spontaneous thought and in high-level cognitive control processes, such as goal/subgoal integration and the manipulation of self-generated thoughts. We therefore propose that the recruitment of lateral RPFC may follow a U-shaped function of cognitive demand: relatively high in low-demand situations conducive to the emergence of spontaneous thought, and in high-demand situations depending on processes supported by this brain region. We used functional magnetic resonance imaging to investigate brain activity while healthy participants performed two tasks, each with three levels of cognitive demands, in a block design. The frequency of task-unrelated thoughts, measured by questionnaire, was highest in the low cognitive demand condition. Low and high cognitive demand conditions were each compared to the intermediate level. Lateral RPFC and superior parietal cortex were recruited in both comparisons, with additional activations specific to each contrast. These results suggest that RPFC is involved both when (a) task demands are low, and the mind wanders, and (b) the task requires goal/subgoal integration and manipulation of self-generated thoughts.

Mind, Body, Spirit: Co-benefits for Mental Health from Climate Change Adaptation and Caring for Country in Remote Aboriginal Australian Communities

New South Wales Public Health Bulletin. May-Jun, 2010  |  Pubmed ID: 20637171

The evident and unresolved health disparity between Aboriginal and other Australians is testament to a history of systematic disenfranchisement. Stigma, lack of appropriate services and the expense of delivering services in remote settings make it impossible to adequately address mental health needs, including suicide, solely using a mainstream medical approach. Nor do mainstream approaches accommodate the relationship between Aboriginal health and connectedness to land, whether traditional or new land, remote or metropolitan. This review describes how caring-for-country projects on traditional lands in remote locations may provide a novel way to achieve the linked goals of climate change adaptation with co-benefits for social and emotional wellbeing.

Distinct Functional Connectivity Associated with Lateral Versus Medial Rostral Prefrontal Cortex: a Meta-analysis

NeuroImage. Dec, 2010  |  Pubmed ID: 20654722

Recent studies have shown that functional connectivity in the human brain may be detected by analyzing the likelihood with which different brain regions are simultaneously activated, or "co-activated", across multiple neuroimaging experiments. We applied this technique to investigate whether distinct subregions within rostral prefrontal cortex (RoPFC) tend to co-activate with distinct sets of brain regions outside RoPFC, in a meta-analysis of 200 activation peaks within RoPFC (approximating Brodmann Area 10) and 1712 co-activations outside this region, drawn from 162 studies. There was little evidence for distinct connectivity between hemispheres or along rostral/caudal or superior/inferior axes. However, there was a clear difference between lateral and medial RoPFC: activation in lateral RoPFC was particularly associated with co-activation in dorsal anterior cingulate, dorsolateral PFC, anterior insula and lateral parietal cortex; medial RoPFC activation was particularly associated with co-activation in posterior cingulate, posterior superior temporal sulcus and temporal pole. These findings are consistent with anatomical studies of connectivity in non-human primates, despite strong cross-species differences in RoPFC. Furthermore, associations between brain regions inside and outside RoPFC were in some cases strongly influenced by the type of task being performed. For example, dorsolateral PFC, anterior cingulate and lateral parietal cortex tended to co-activate with lateral RoPFC in most tasks but with medial RoPFC in tasks involving mentalizing. These results suggest the importance of changes in effective connectivity in the performance of cognitive tasks.

On Firm Ground: IP Protection of Therapeutic Nanoparticles

Nature Biotechnology. Dec, 2010  |  Pubmed ID: 21139609

Looking to the Future: Automatic Regulation of Attention Between Current Performance and Future Plans

Neuropsychologia. Jul, 2011  |  Pubmed ID: 21315748

We investigated neuro-cognitive mechanisms involved with coordination of attention between current task performance and future action plans in prospective memory. We developed a novel task paradigm with continuous performance of a prospective memory task, where trial intervals of prospective memory targets were systematically manipulated in a periodic cycle of expanding and contracting target intervals. We found that subjects' behaviour was significantly modulated without awareness of this temporal sequence of the targets: remembering to perform a prospective memory response to target events was more successful and faster in the expanding target interval phase, at the cost of lower and slower performance of ongoing tasks, while an opposite direction of this trade-off effect was observed in the contracting target interval phase. By using functional magnetic resonance imaging (fMRI), we identified the similar trade-off effect in activations in the anterior medial prefrontal cortices (activation elevation at the target responses as well as deactivation at the ongoing responses in the expanding phase as compared with the contracting phase). The opposite direction of the trade-off was observed in the anterior cingulate cortex. These results show a clear case in which attention between current task performance and future action plans in prospective memory tasks is automatically regulated without particular task instructions or strategic control processes initiated by subjects. We suggest that medial areas of the frontal cortex specifically mediate the automatic coordination of attentional resources between current task performance and future action plans.

Functional Neuroimaging Studies of Prospective Memory: What Have We Learnt So Far?

Neuropsychologia. Jul, 2011  |  Pubmed ID: 21329712

The complexity of the behaviour described by the term "prospective memory" meant that it was not at all clear, when the earliest studies were conducted, that this would prove a fruitful area for neuroimaging study. However, a consistent relation rapidly emerged between activation in rostral prefrontal cortex (approximating Brodmann Area 10) and performance of prospective memory paradigms. This consistency has greatly increased the accumulation of findings, since each study has offered perspectives on the previous ones. Considerable help too has come from broad agreement between functional neuroimaging findings and those from other methods (e.g. human lesion studies, electrophysiology). The result has been a quite startling degree of advance given the relatively few studies that have been conducted. These findings are summarised, along with those from other brain regions, and new directions suggested. Key points are that there is a medial-lateral dissociation within rostral PFC. Some (but not all) regions of medial rostral PFC are typically more active during performance of the ongoing task only, and lateral aspects are relatively more active during conditions involving delayed intentions. Some of these rostral PFC activations seem remarkably insensitive to the form of stimulus material presented, the nature of the ongoing task, the specifics of the intention, how easy or hard the PM cue is to detect, or the intended action is to recall. However there are other regions within rostral PFC where haemodynamic changes vary with alterations in these, and other, aspects of prospective memory paradigms. It is concluded that rostral PFC most likely plays a super-ordinate role during many stages of creating, maintaining and enacting delayed intentions, which in some cases may be linked to recent evidence showing that this brain region is involved in the control of stimulus-oriented vs. stimulus-independent attending. Other key brain regions activated during prospective memory paradigms appear to be the parietal lobe, especially Brodmann Area (BA) 40 and precuneus (BA 7), and the anterior cingulate (BA 32). These regions are often co-activated with lateral rostral PFC across a wide range of tasks, not just those involving prospective memory.

The Role of Rostral Prefrontal Cortex in Prospective Memory: a Voxel-based Lesion Study

Neuropsychologia. Jul, 2011  |  Pubmed ID: 21371485

Patients with lesions in rostral prefrontal cortex (PFC) often experience problems in everyday-life situations requiring multitasking. A key cognitive component that is critical in multitasking situations is prospective memory, defined as the ability to carry out an intended action after a delay period filled with unrelated activity. The few functional imaging studies investigating prospective memory have shown consistent activation in both medial and lateral rostral PFC but also in more posterior prefrontal regions and non-frontal regions. The aim of this study was to determine regions that are necessary for prospective memory performance, using the human lesion approach. We designed an experimental paradigm allowing us to assess time-based (remembering to do something at a particular time) and event-based (remembering to do something in a particular situation) prospective memory, using two types of material, words and pictures. Time estimation tasks and tasks controlling for basic attention, inhibition and multiple instructions processing were also administered. We examined brain-behaviour relationships with a voxelwise lesion method in 45 patients with focal brain lesions and 107 control subjects using this paradigm. The results showed that lesions in the right polar prefrontal region (in Brodmann area 10) were specifically associated with a deficit in time-based prospective memory tasks for both words and pictures. This deficit could not be explained by impairments in basic attention, detection, inhibition or multiple instruction processing, and there was also no deficit in event-based prospective memory conditions. In addition to their prospective memory difficulties, these polar prefrontal patients were significantly impaired in time estimation ability compared to other patients. The same region was found to be involved using both words and pictures, suggesting that right rostral PFC plays a material nonspecific role in prospective memory. This is the first lesion study showing that rostral PFC is crucial for time-based prospective memory. The findings suggest that time-based and event-based prospective memory might be supported at least in part by distinct brain regions. Two particularly plausible explanations for the deficit rest upon a possible role for polar prefrontal structures in supporting in time estimation, and/or in retrieving an intention to act. More broadly, the results are consistent with the view that the deficit of rostral patients in multitasking situations might at least in part be explained by a deficit in prospective memory.

A Neural Mechanism Mediating the Impact of Episodic Prospection on Farsighted Decisions

The Journal of Neuroscience : the Official Journal of the Society for Neuroscience. May, 2011  |  Pubmed ID: 21543607

Humans can vividly imagine possible future events. This faculty, episodic prospection, allows the simulation of distant outcomes and desires. Here, we provide evidence for the adaptive function of this capacity and elucidate its neuronal basis. Participants either imagined specific events of spending money (e.g., £ 35 in 180 days at a pub), or merely estimated what the money could purchase in the scenario. Imagining the future biased subsequent monetary decisions toward choices associated with a higher long-term pay-off. It thus effectively attenuated temporal discounting, i.e., the propensity to devalue rewards with a delay until delivery. Using functional magnetic resonance imaging, we implicate the medial rostral prefrontal cortex (mrPFC) in this effect. Blood oxygen level-dependent signal in this region predicted future-oriented choices on a trial-by-trial basis. Activation reflected the reward magnitude of imagined episodes, and greater reward sensitivity was related to less discounting. This effect was also associated with increased mrPFC-hippocampal coupling. The data suggest that mrPFC uses information conveyed by the hippocampus to represent the undiscounted utility of envisaged events. The immediate experience of the delayed reward value might then bias toward farsighted decisions.

Frontopolar Cortex: Constraints for Theorizing

Trends in Cognitive Sciences. Jun, 2011  |  Pubmed ID: 21571576

Rostral Prefrontal Cortex and the Focus of Attention in Prospective Memory

Cerebral Cortex (New York, N.Y. : 1991). Aug, 2012  |  Pubmed ID: 21976356

Prospective memory (PM) denotes the function to realize intentions after a delay while being immersed in distracting ongoing (OG) activity. Here, we scrutinize the often-reported involvement of rostral prefrontal cortex (rPFC; approximating Brodmann area 10) in such situations: This region might mediate attention between external stimuli and the internally maintained intention, that is, between stimulus-oriented (SO) and stimulus-independent (SI) processing. Using functional magnetic resonance imaging (fMRI) we orthogonally crossed 1) PM versus OG activity only, with 2) SO versus SI attention. In support of the hypothesis, common regions of medial rPFC exhibited greater blood oxygen level-dependent (BOLD) signal for the contrasts of both OG task only versus PM and SO versus SI attending. However, activation related to the former contrast extended more superiorly, suggesting a functional gradient along a dorsal-ventral axis within this region. Moreover, region-of-interest analyses revealed that PM versus OG task only was associated with greater BOLD signal in left lateral rPFC, reflecting the requirement to maintain delayed intentions. Distinct aspects of this region were also transiently engaged at transitions between SO and SI conditions. These results are consistent with the hypothesis that some of the rostral prefrontal signal changes associated with PM performance reflect relative differences in SO versus SI processing.

Dissociation Between Verbal Response Initiation and Suppression After Prefrontal Lesions

Cerebral Cortex (New York, N.Y. : 1991). Oct, 2012  |  Pubmed ID: 22095216

Some of the most striking symptoms after prefrontal damage are reduction of behavioral initiation and inability to suppress automatic behaviors. However, the relation between these 2 symptoms and the location of the lesions that cause them are not well understood. This study investigates the cerebral correlates of initiation and suppression abilities assessed by the Hayling Sentence Completion Test, using the human lesion approach. Forty-five patients with focal brain lesions and 110 healthy matched controls were examined. We combined a classical group approach with 2 voxel-based lesion methods. The results show several critical prefrontal regions to Hayling Test performance, associated with either common or differential impairment in "initiation" and "suppression" conditions. A crucial role for medial rostral prefrontal cortex (BA 10) in the initiation condition was shown by both group and lesion-mapping methods. A posterior inferolateral lesion provoked both initiation and suppression slowness, although to different degrees. An orbitoventral region was associated with errors in the suppression condition. These findings are important for clinical practice since they indicate that the brain regions required to perform a widely used and sensitive neuropsychological test but also shed light on the regions crucial for distinct components of adaptative behaviors, in particular, rostral prefrontal cortex.

Does "task Difficulty" Explain "task-induced Deactivation?"

Frontiers in Psychology. 2012  |  Pubmed ID: 22539930

The "default mode network" is commonly described as a set of brain regions in which activity is suppressed during relatively demanding, or difficult, tasks. But what sort of tasks are these? We review some of the contrasting ways in which a task might be assessed as being difficult, such as error rate, response time, propensity to interfere with performance of other tasks, and requirement for transformation of internal representations versus accumulation of perceptual information. We then describe a fMRI study in which 18 participants performed two "stimulus-oriented" tasks, where responses were directly cued by visual stimuli, alongside a "stimulus-independent" task, with a greater reliance on internally generated information. When indexed by response time and error rate, the stimulus-independent task was intermediate in difficulty between the two stimulus-oriented tasks. Nevertheless, BOLD signal in medial rostral prefrontal cortex (MPFC) - a prominent part of the default mode network - was reduced in the stimulus-independent condition in comparison with both the more difficult and the less difficult stimulus-oriented conditions. By contrast, other regions of the default mode network showed greatest deactivation in the difficult stimulus-oriented condition. There was therefore significant functional heterogeneity between different default mode regions. We conclude that task difficulty - as measured by response time and error rate - does not provide an adequate account of signal change in MPFC. At least in some circumstances, a better predictor of MPFC activity is the requirement of a task for transformation and manipulation of internally represented information, with greatest MPFC activity in situations predominantly requiring attention to perceptual information.

Use of the Multiple Errands Test-Simplified Version in the Assessment of Suboptimal Effort

Neuropsychological Rehabilitation. 2012  |  Pubmed ID: 22672068

Most measures of suboptimal effort focus on short-term learning; fewer studies have considered non-memory feigned cognitive impairment. This study investigated the utility of the Multiple Errands Test - Simplified Version (MET-SV) in the detection of feigned executive functioning impairment. Performance of simulating malingerers (N = 47) was compared to acquired brain injury (N = 46) and neurologically healthy control groups (N = 50). Although simulating malingerers were successful at feigning a realistic level of impairment compared to the brain injury group, there were significant differences regarding pattern of performance. A logistic regression model successfully classified 84% of simulating malingerers and 74.5% of brain injured individuals. Receiver Operating Characteristic (ROC) analysis supported the discriminatory power of the model. The current study is unique in yielding some understanding of the real-life observation of suspected malingerers compared to individuals with genuine cognitive difficulties. Results suggest the MET-SV can contribute to the clinical assessment of individuals suspected of suboptimal effort in the domain of executive functioning. Further research is needed to establish whether the MET-SV can be reliably used in medico-legal settings.

Predicting the Impacts of Bioenergy Production on Farmland Birds

The Science of the Total Environment. Apr, 2014  |  Pubmed ID: 24463022

Meeting European renewable energy production targets is expected to cause significant changes in land use patterns. With an EU target of obtaining 20% of energy consumption from renewable sources by 2020, national and local policy makers need guidance on the impact of potential delivery strategies on ecosystem goods and services to ensure the targets are met in a sustainable manner. Within agroecosystems, models are available to explore consequences of such policy decisions for food, fuel and fibre production but few can describe the effect on biodiversity. This paper describes the integration and application of a farmland bird population model within a geographical information system (GIS) to explore the consequences of land use changes arising from different strategies to meet renewable energy production targets. Within a 16,000 ha arable dominated case study area in England, the population growth rates of 19 farmland bird species were predicted under baseline land cover, a scenario maximising wheat production for bioethanol, and a scenario focused on mix of bioenergy sources. Both scenarios delivered renewable energy production targets for the region (>12 kWh per person per day) but, despite differences in resultant landscape composition, the response of the farmland bird community as a whole to each scenario was small and broadly similar. However, this similarity in overall response masked significant intra- and inter-specific variations across the study area and between scenarios suggesting contrasting mechanisms of impact and highlighting the need for context dependent, species-level assessment of land use change impacts. This framework provides one of the first systematic attempts to spatially model the effect of policy driven land use change on the population dynamics of a suite of farmland birds. The GIS framework also facilitates its integration with other ecosystem service models to explore wider synergies and trade offs arising from national or local policy interventions.

Managing Declining Yields from Ageing Tea Plantations

Journal of the Science of Food and Agriculture. Jun, 2014  |  Pubmed ID: 24464583

Strong growth in the demand for tea requires further increases in the productivity of plantations. Declining or stagnant yields are commonly observed in older plantations. Possible controlling factors for yield decline are reviewed including ageing of plants, chronic disease and sub-optimal soil conditions such as excess soil acidity and low soil organic matter. Management options for addressing these factors are evaluated, including replanting. A systematic approach to decision-making about replanting is presented. Practice for replanting is reviewed and it is concluded that evidence to support a general case for replanting is limited, unless based on the introduction of more productive clones and/or better plant spacing.

Increased Set Shifting Costs in Fasted Healthy Volunteers

PloS One. 2014  |  Pubmed ID: 25025179

We investigated the impact of temporary food restriction on a set shifting task requiring participants to judge clusters of pictures against a frequently changing rule. 60 healthy female participants underwent two testing sessions: once after fasting for 16 hours and once in a satiated state. Participants also completed a battery of questionnaires (Hospital Anxiety and Depression Scale [HADS]; Persistence, Perseveration and Perfectionism Questionnaire [PPPQ-22]; and Eating Disorders Examination Questionnaire [EDE-Q6]). Set shifting costs were significantly increased after fasting; this effect was independent of self-reported mood and perseveration. Furthermore, higher levels of weight concern predicted a general performance decrement under conditions of fasting. We conclude that relatively short periods of fasting can lead to set shifting impairments. This finding may have relevance to studies of development, individual differences, and the interpretation of psychometric tests. It also could have implications for understanding the etiology and maintenance of eating disorders, in which impaired set shifting has been implicated.

Time Trends for Injuries and Illness, and Their Relation to Performance in the National Basketball Association

Journal of Science and Medicine in Sport / Sports Medicine Australia. May, 2015  |  Pubmed ID: 24908360

To survey injury/illness in the National Basketball Association over a 25-year period and examine the relationship of injury/illness to team performance.

The Association Between Knee Extensor Force Steadiness, Force Accuracy, and Mobility in Older Adults Who Have Fallen

Journal of Geriatric Physical Therapy (2001). Feb, 2015  |  Pubmed ID: 25695470

Older adults often experience impaired mobility, lower extremity muscle weakness, and increased fall risk. Furthermore, when older adults perform tasks that require control of submaximal force, impairments in their ability to maintain steady and accurate force output have been reported. Such problems may be related to deteriorating levels of mobility, particularly in older adults who have fallen.

Effects of Practice on Variability of Muscle Force

Perceptual and Motor Skills. Apr, 2015  |  Pubmed ID: 25799026

The motor skill required to decrease the variability in muscle force steadiness can be challenging. The purposes of this study were to determine whether muscle force steadiness improved following repeated trials and whether the number of trials varied for healthy younger adults, healthy older adults, and older adults who have fallen to obtain stable muscle force steadiness measures. Sixty participants performed 30 concentric and eccentric contractions of the knee extensors on an isokinetic dynamometer. Each group had significant improvements in muscle force steadiness and obtained stable measures within six to nine trials. Healthy younger and older adults, and older adults who have fallen, can improve muscle force steadiness. These findings provide a framework for methodological approaches when testing steadiness in varying populations.

Evaluation of Bone Marrow Reticulin in Patients with Chronic Immune Thrombocytopenia Treated with Eltrombopag: Data from the EXTEND Study

American Journal of Hematology. Jul, 2015  |  Pubmed ID: 25801698

Thrombopoietin receptor agonists, which raise platelet counts in patients with chronic immune thrombocytopenia, may be associated with increases in bone marrow (BM) reticulin. Patients with chronic immune thrombocytopenia participating in the Eltrombopag Extended Dosing (EXTEND) study underwent BM biopsies to identify clinically relevant BM fibrosis-related increases. Specimens were centrally reviewed by 2 hematopathologists. Two hundred thirty-two biopsy specimens were collected from 117 patients treated for ≤5.5 years. Moderate to marked reticulin fibrosis was found in 2 patients. After withdrawing from the study, the biopsy of 1 patient reverted to normal. There were no other pathologic changes identified among on-treatment specimens, and no pattern of abnormal reticulin deposition associated with eltrombopag treatment was evident.

Does Faux Pas Detection in Adult Autism Reflect Differences in Social Cognition or Decision-Making Abilities?

Journal of Autism and Developmental Disorders. Aug, 2015  |  Pubmed ID: 26276266

43 typically-developed adults and 35 adults with ASD performed a cartoon faux pas test. Adults with ASD apparently over-detected faux pas despite good comprehension abilities, and were generally slower at responding. Signal detection analysis demonstrated that the ASD participants had significantly greater difficulty detecting whether a cartoon depicted a faux pas and showed a liberal response bias. Test item analysis demonstrated that the ASD group were not in agreement with a reference control group (n = 69) about which non-faux pas items were most difficult. These results suggest that the participants with ASD had a primary problem with faux pas detection, but that there is another factor at work, possibly compensatory, that relates to their choice of a liberal response criterion.

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