Publications
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Cannon R, Kerson C, Hampshire A, et al., 2012, Pilot Data Assessing the Functional Integrity of the Default Network in Adult ADHD with fMRI and sLORETA, Journal of Neurotherapy
Hampshire A, Highfield RR, Parkin BL, et al., 2012, Fractionating human intelligence, Neuron, Vol: 76, Pages: 1225-1237, ISSN: 1097-4199
What makes one person more intellectually able than another? Can the entire distribution of human intelligence be accounted for by just one general factor? Is intelligence supported by a single neural system? Here, we provide a perspective on human intelligence that takes into account how general abilities or "factors" reflect the functional organization of the brain. By comparing factor models of individual differences in performance with factor models of brain functional organization, we demonstrate that different components of intelligence have their analogs in distinct brain networks. Using simulations based on neuroimaging data, we show that the higher-order factor "g" is accounted for by cognitive tasks corecruiting multiple networks. Finally, we confirm the independence of these components of intelligence by dissociating them using questionnaire variables. We propose that intelligence is an emergent property of anatomically distinct cognitive systems, each of which has its own capacity.
Hampshire A, Chaudhry AM, Owen AM, et al., 2012, Dissociable roles for lateral orbitofrontal cortex and lateral prefrontal cortex during preference driven reversal learning, Neuroimage, Vol: 59, Pages: 4102-4112, ISSN: 1095-9572
One of the archetypal task manipulations known to depend on frontal-lobe function is reversal learning, where a dominant response must be overridden due to changes in the contingencies relating stimuli, responses, and environmental feedback. Previous studies have indicated that the lateral prefrontal cortex (LPFC), the lateral orbitofrontal cortex (LOFC), the anterior cingulate cortex (ACC), and the caudate nucleus (CN) all contribute to reversal learning. However, the exact contributions that they make during this cognitively complex task remain poorly defined. Here, using functional magnetic resonance imaging, we examine which of the cognitive processes that contribute to the performance of a reversal best predicts the pattern of activation within distinct sub-regions of the frontal lobes. We demonstrate that during reversal learning the LOFC is particularly sensitive to the implementation of the reversal, whereas the LPFC is recruited more generally during attentional control. By contrast, the ACC and CN respond when new searches are initiated regardless of whether the previous response is available, whilst medial orbitofrontal cortex (MOFC) activity is correlated with the positive affect of feedback. These results accord well with the hypothesis that distinct components of adaptable behaviour are supported by anatomically distinct components of the executive system.
Hampshire A, Thompson R, Duncan J, et al., 2011, Lateral prefrontal cortex subregions make dissociable contributions during fluid reasoning, Cereb Cortex, Vol: 21, Pages: 1-10, ISSN: 1460-2199
Reasoning is a key component of adaptable "executive" behavior and is known to depend on a network of frontal and parietal brain regions. However, the mechanisms by which this network supports reasoning and adaptable behavior remain poorly defined. Here, we examine the relationship between reasoning, executive control, and frontoparietal function in a series of nonverbal reasoning experiments. Our results demonstrate that, in accordance with previous studies, a network of frontal and parietal brain regions is recruited during reasoning. Our results also reveal that this network can be fractionated according to how different subregions respond when distinct reasoning demands are manipulated. While increased rule complexity modulates activity within a right lateralized network including the middle frontal gyrus and the superior parietal cortex, analogical reasoning demand-or the requirement to remap rules on to novel features-recruits the left inferior rostrolateral prefrontal cortex and the lateral occipital complex. In contrast, the posterior extent of the inferior frontal gyrus, associated with simpler executive demands, is not differentially sensitive to rule complexity or analogical demand. These findings accord well with the hypothesis that different reasoning demands are supported by different frontal and parietal subregions.
Woolgar A, Hampshire A, Thompson R, et al., 2011, Adaptive coding of task-relevant information in human frontoparietal cortex, J Neurosci, Vol: 31, Pages: 14592-14599, ISSN: 1529-2401
Frontoparietal cortex is thought to be essential for flexible behavior, but the mechanism for control remains elusive. Here, we demonstrate a potentially critical property of this cortex: its dynamic configuration for coding of task-critical information. Using multivoxel pattern analysis of human functional imaging data, we demonstrate an adaptive change in the patterns of activation coding task-relevant stimulus distinctions. When task demands made perceptual information more difficult to discriminate, frontoparietal regions showed increased coding of this information. Visual cortices showed the opposite result: a weaker representation of perceptual information in line with the physical change in the stimulus. On a longer timescale, a rebalancing of coding was also seen after practice, with a diminished representation of task rules as they became familiar. The results suggest a flexible neural system, exerting cognitive control in a wide range of tasks by adaptively representing the task features most challenging for successful goal-directed behavior.
Cannon R, Kerson C, Hampshire A, 2011, sLORETA and fMRI Detection of Medial Prefrontal Default Network Anomalies in Adult ADHD, Journal of Neurotherapy
Huntley J, Bor D, Hampshire A, et al., 2011, Working memory task performance and chunking in early Alzheimer's disease, Br J Psychiatry, Vol: 198, Pages: 398-403, ISSN: 1472-1465
BACKGROUND: Chunking is a powerful encoding strategy that significantly improves working memory performance in normal young people. AIMS: To investigate chunking in patients with mild Alzheimer's disease and in a control group of elderly people without cognitive impairment. METHOD: People with mild Alzheimer's disease (n = 28) were recruited and divided according to Mini-Mental State Examination score into mild and very mild disease groups. A control group of 15 elderly individuals was also recruited. All participants performed digit and spatial working memory tasks requiring either unstructured sequences or structured sequences (which encourage chunking of information) to be recalled. RESULTS: The control group and both disease groups performed significantly better on structured trials of the digit working memory tasks, indicating successful use of chunking strategies to improve verbal working memory performance. The control and very mild disease groups also performed significantly better on structured trials of the spatial task, whereas those with mild disease demonstrated no significant difference between the structured and unstructured spatial conditions. CONCLUSIONS: The ability to use chunking as an encoding strategy to improve verbal working memory performance is preserved at the mild stage of Alzheimer's disease, whereas use of chunking to improve spatial working memory is impaired by this stage. Simple training in the use of chunking might be a beneficial therapeutic strategy to prolong working memory functioning in patients at the earliest stage of Alzheimer's disease.
Kempton MJ, Ettinger U, Foster R, et al., 2011, Dehydration affects brain structure and function in healthy adolescents, Hum Brain Mapp, Vol: 32, Pages: 71-79, ISSN: 1097-0193
It was recently observed that dehydration causes shrinkage of brain tissue and an associated increase in ventricular volume. Negative effects of dehydration on cognitive performance have been shown in some but not all studies, and it has also been reported that an increased perceived effort may be required following dehydration. However, the effects of dehydration on brain function are unknown. We investigated this question using functional magnetic resonance imaging (fMRI) in 10 healthy adolescents (mean age = 16.8, five females). Each subject completed a thermal exercise protocol and nonthermal exercise control condition in a cross-over repeated measures design. Subjects lost more weight via perspiration in the thermal exercise versus the control condition (P < 0.0001), and lateral ventricle enlargement correlated with the reduction in body mass (r = 0.77, P = 0.01). Dehydration following the thermal exercise protocol led to a significantly stronger increase in fronto-parietal blood-oxygen-level-dependent (BOLD) response during an executive function task (Tower of London) than the control condition, whereas cerebral perfusion during rest was not affected. The increase in BOLD response after dehydration was not paralleled by a change in cognitive performance, suggesting an inefficient use of brain metabolic activity following dehydration. This pattern indicates that participants exerted a higher level of neuronal activity in order to achieve the same performance level. Given the limited availability of brain metabolic resources, these findings suggest that prolonged states of reduced water intake may adversely impact executive functions such as planning and visuo-spatial processing.
Schweizer S, Hampshire A, Dalgleish T, 2011, Extending brain-training to the affective domain: increasing cognitive and affective executive control through emotional working memory training, PLoS One, Vol: 6, ISSN: 1932-6203
So-called 'brain-training' programs are a huge commercial success. However, empirical evidence regarding their effectiveness and generalizability remains equivocal. This study investigated whether brain-training (working memory [WM] training) improves cognitive functions beyond the training task (transfer effects), especially regarding the control of emotional material since it constitutes much of the information we process daily. Forty-five participants received WM training using either emotional or neutral material, or an undemanding control task. WM training, regardless of training material, led to transfer gains on another WM task and in fluid intelligence. However, only brain-training with emotional material yielded transferable gains to improved control over affective information on an emotional Stroop task. The data support the reality of transferable benefits of demanding WM training and suggest that transferable gains across to affective contexts require training with material congruent to those contexts. These findings constitute preliminary evidence that intensive cognitively demanding brain-training can improve not only our abstract problem-solving capacity, but also ameliorate cognitive control processes (e.g. decision-making) in our daily emotive environments.
Chamberlain SR, Hampshire A, Menzies L, et al., 2010, Reduced brain white matter integrity in trichotillomania: a diffusion tensor imaging study., Archives of General Psychiatry, Vol: 67, Pages: 965-965, ISSN: 0003-990X
CONTEXT: Trichotillomania is an Axis I disorder characterized by repetitive, pathological hair pulling. OBJECTIVE: To assess the integrity of white matter tracts in subjects with the disorder. DESIGN: Between-group comparison using permutation cluster analysis, with stringent correction for multiple comparisons. SETTING: Academic psychiatry department. PARTICIPANTS: Eighteen volunteers meeting DSM-IV criteria for trichotillomania and 19 healthy control subjects. MAIN OUTCOME MEASURES: Fractional anisotropy (measured using diffusion tensor imaging), trichotillomania disease severity (Massachusetts General Hospital Hairpulling Scale score), and dysphoria (Montgomery-Asberg Depression Rating Scale score). RESULTS: Subjects with trichotillomania exhibited significantly reduced fractional anisotropy in anterior cingulate, presupplementary motor area, and temporal cortices. Fractional anisotropy did not correlate significantly with trichotillomania disease severity or depressive mood scores. CONCLUSIONS: These data implicate disorganization of white matter tracts involved in motor habit generation and suppression, along with affective regulation, in the pathophysiology of trichotillomania.
Gruszka A, Hampshire A, Owen AM, 2010, Learned Irrelevance Revisited: Pathology-Based Individual Differences, Normal Variation and Neural Correlates, Handbook of Individual Differences in Cognition, Editors: Gruszka, Matthews, Szymura, New York, Publisher: Springer
Hampshire A, Owen A, 2010, Clinical studies of attention and learning, Attention and associative learning: from brain to behaviou, Editors: Mitchell, Le Pelley, Oxford, Publisher: Oxfor University Press
Owen AM, Hampshire A, Grahn JA, et al., 2010, Putting brain training to the test, Nature, Vol: 465, Pages: 775-778, ISSN: 1476-4687
'Brain training', or the goal of improved cognitive function through the regular use of computerized tests, is a multimillion-pound industry, yet in our view scientific evidence to support its efficacy is lacking. Modest effects have been reported in some studies of older individuals and preschool children, and video-game players outperform non-players on some tests of visual attention. However, the widely held belief that commercially available computerized brain-training programs improve general cognitive function in the wider population in our opinion lacks empirical support. The central question is not whether performance on cognitive tests can be improved by training, but rather, whether those benefits transfer to other untrained tasks or lead to any general improvement in the level of cognitive functioning. Here we report the results of a six-week online study in which 11,430 participants trained several times each week on cognitive tasks designed to improve reasoning, memory, planning, visuospatial skills and attention. Although improvements were observed in every one of the cognitive tasks that were trained, no evidence was found for transfer effects to untrained tasks, even when those tasks were cognitively closely related.
Hampshire A, Chamberlain SR, Monti MM, et al., 2010, The role of the right inferior frontal gyrus: inhibition and attentional control, Neuroimage, Vol: 50, Pages: 1313-1319, ISSN: 1095-9572
There is growing interest regarding the role of the right inferior frontal gyrus (RIFG) during a particular form of executive control referred to as response inhibition. However, tasks used to examine neural activity at the point of response inhibition have rarely controlled for the potentially confounding effects of attentional demand. In particular, it is unclear whether the RIFG is specifically involved in inhibitory control, or is involved more generally in the detection of salient or task relevant cues. The current fMRI study sought to clarify the role of the RIFG in executive control by holding the stimulus conditions of one of the most popular response inhibition tasks-the Stop Signal Task-constant, whilst varying the response that was required on reception of the stop signal cue. Our results reveal that the RIFG is recruited when important cues are detected, regardless of whether that detection is followed by the inhibition of a motor response, the generation of a motor response, or no external response at all.
Berry E, Hampshire A, Rowe J, et al., 2009, The neural basis of effective memory therapy in a patient with limbic encephalitis, J Neurol Neurosurg Psychiatry, Vol: 80, Pages: 1202-1205, ISSN: 1468-330X
BACKGROUND: An fMRI study is described in which a postencephalitic woman with amnesia used a wearable camera which takes photographs passively, without user intervention, to record and review recent autobiographical events. "SenseCam" generates hundreds of images which can subsequently be reviewed quickly or one by one. RESULTS: Memory for a significant event was improved substantially when tested after 4.5 weeks, if the patient viewed SenseCam images of the event every 2 days for 3 weeks. In contrast, after only 3.5 weeks, her memory was at chance levels for a similarly significant event which was reviewed equally often, but using a written diary. During the fMRI scan, the patient viewed images of these two events, plus images of an unrehearsed event and images from a novel "control" event that she had never experienced. There was no difference in behavioural responses or in activation when the unrehearsed and novel conditions were compared. Relative to the written-rehearsed condition, successful recognition of the images in the SenseCam-rehearsed condition was associated with activation of frontal and posterior cortical regions associated with normal episodic memory. CONCLUSION: SenseCam images may provide powerful cues that trigger the recall and consolidation of stored but inaccessible memories.
Chamberlain SR, Hampshire A, Müller U, et al., 2009, Atomoxetine Modulates Right Inferior Frontal Activation During Inhibitory Control: A Pharmacological Functional Magnetic Resonance Imaging Study, Biological Psychiatry, Vol: 65, Pages: 550-555, ISSN: 0006-3223
BACKGROUND: Atomoxetine, a selective noradrenaline reuptake inhibitor (SNRI) licensed for the treatment of attention-deficit/hyperactivity disorder (ADHD), has been shown to improve response inhibition in animals, healthy volunteers, and adult patients. However, the mechanisms by which atomoxetine improves inhibitory control have yet to be determined. METHODS: The effects of atomoxetine (40 mg) were measured with a stop-signal functional magnetic resonance imaging (fMRI) paradigm in 19 healthy volunteers, in a within-subject, double-blind, placebo-controlled design. RESULTS: Atomoxetine improved inhibitory control and increased activation in the right inferior frontal gyrus when volunteers attempted to inhibit their responses (irrespective of success). Plasma levels of drug correlated significantly with right inferior frontal gyrus activation only during successful inhibition. CONCLUSIONS: These results show that atomoxetine exerts its beneficial effects on inhibitory control via modulation of right inferior frontal function, with implications for understanding and treating inhibitory dysfunction of ADHD and other disorders.
Owen A, Hampshire A, 2009, The mid-ventrolateral frontal cortex and attentional control, Neuroimaging in Human Memory: Linking cognitive processes to neural systems., Editors: Rosler, Ranganath, Roder, Kluwe, Oxford, Publisher: OUP Oxford
Piech RM, Hampshire A, Owen AM, et al., 2009, Modulation of cognitive flexibility by hunger and desire, Cognition & Emotion
Hampshire A, Thompson R, Duncan J, et al., 2009, Selective tuning of the right inferior frontal gyrus during target detection, Cogn Affect Behav Neurosci, Vol: 9, Pages: 103-112, ISSN: 1530-7026
In the human brain, a network of frontal and parietal regions is commonly recruited during tasks that demand the deliberate, focused control of thought and action. Previously, using a simple target detection task, we reported striking differences in the selectivity of the BOLD response in anatomically distinct subregions of this network. In particular, it was observed that the right inferior frontal gyrus (IFG) followed a tightly tuned function, selectively responding only to the current target object. Here, we examine this functional specialization further, using adapted versions of our original task. Our results demonstrate that the response of the right IFG to targets is a strong and replicable phenomenon. It occurs under increased attentional load, when targets and distractors are equally frequent, and when controlling for inhibitory processes. These findings support the hypothesis that the right IFG responds selectively to those items that are of the most relevance to the currently intended task schema.
Passamonti L, Rowe JB, Ewbank M, et al., 2008, Connectivity from the ventral anterior cingulate to the amygdala is modulated by appetitive motivation in response to facial signals of aggression, NeuroImage, Vol: 43, Pages: 562-570, ISSN: 1053-8119
For some people facial expressions of aggression are intimidating, for others they are perceived as provocative, evoking an aggressive response. Identifying the key neurobiological factors that underlie this variation is fundamental to our understanding of aggressive behaviour. The amygdala and the ventral anterior cingulate cortex (ACC) have been implicated in aggression. Using functional magnetic resonance imaging (fMRI), we studied how the interaction between these regions is influenced by the drive to obtain reward (reward-drive or appetitive motivation), a personality trait consistently associated with aggression. Two distinct techniques showed that the connectivity between the ventral ACC and the amygdala was strongly correlated with personality, with high reward-drive participants displaying reduced negative connectivity. Furthermore, the direction of this effect was restricted from ventral ACC to the amygdala but not vice versa. The personality-mediated variation in the pathway from the ventral anterior cingulate cortex to the amygdala provides an account of why signals of aggression are interpreted as provocative by some individuals more than others.
Hampshire A, Gruszka A, Fallon SJ, et al., 2008, Inefficiency in self-organized attentional switching in the normal aging population is associated with decreased activity in the ventrolateral prefrontal cortex, J Cogn Neurosci, Vol: 20, Pages: 1670-1686, ISSN: 0898-929X
Studies of the aging brain have demonstrated that areas of the frontal cortex, along with their associated top-down executive control processes, are particularly prone to the neurodegenerative effects of age. Here, we investigate the effects of aging on brain and behavior using a novel task, which allows us to examine separate components of an individual's chosen strategy during routine problem solving. Our findings reveal that, contrary to previous suggestions of a specific decrease in cognitive flexibility, older participants show no increased level of perseveration to either the recently rewarded object or the recently relevant object category. In line with this lack of perseveration, lateral and medial regions of the orbito-frontal cortex, which are associated with inhibitory control and reward processing, appear to be functionally intact. Instead, a general loss of efficient problem-solving strategy is apparent with a concomitant decrease in neural activity in the ventrolateral prefrontal cortex and the posterior parietal cortex. The dorsolateral prefrontal cortex is also affected during problem solving, but age-related decline within this region appears to occur at a later stage.
Williams-Gray CH, Hampshire A, Barker RA, et al., 2008, Attentional control in Parkinson's disease is dependent on COMT val 158 met genotype, Brain, Vol: 131, Pages: 397-408, ISSN: 1460-2156
Cognitive deficits occur even in the earliest stages of Parkinson's disease. Some such deficits are known to relate to dysfunction in dopaminergic frontostriatal networks, and may be influenced by a common functional polymorphism (val(158)met) within the catechol O-methyltransferase (COMT) gene. Abnormal attentional shifting behaviour is an important and well-recognized cognitive problem in PD, but nonetheless its precise cognitive and neural basis remains unclear. Here we explored this impairment in an fMRI study employing a recently developed cognitive task designed to fractionate components of attentional control. We investigated the impact of the COMT val(158)met genotype and dopaminergic medication on both patterns of behaviour and associated brain activation in 29 medicated patients with early PD. Genotype had a critical impact on task strategy: whilst patients with high activity COMT genotypes (val/val) adopted a typical approach of preferentially shifting attention within rather than between dimensions, those with low activity genotypes (met/met) failed to adopt such a strategy, suggesting an inability to form an attentional 'set'. Moreover, this behaviour was associated with significant underactivation across the frontoparietal attentional network. Furthermore, we demonstrated an interactive effect of COMT genotype and dopaminergic medication on task performance and BOLD response. Hence we have shown for the first time that attentional control in PD is critically determined by genetic and pharmacological influences on dopaminergic activity in frontoparietal networks. This has important implications for understanding the neurobiological basis of attentional control, and highlights the risk of medication-induced cognitive dysfunction in certain genotypic groups of PD patients, which may ultimately impact on clinical practice.
Hampshire A, Thompson R, Duncan J, et al., 2008, The target selective neural response--similarity, ambiguity, and learning effects, PLoS One, Vol: 3, ISSN: 1932-6203
A network of frontal and parietal brain regions is commonly recruited during tasks that require the deliberate 'top-down' control of thought and action. Previously, using simple target detection, we have demonstrated that within this frontoparietal network, the right ventrolateral prefrontal cortex (VLPFC) in particular is sensitive to the presentation of target objects. Here, we use a range of target/non-target morphs to plot the target selective response within distinct frontoparietal sub-regions in greater detail. The increased resolution allows us to examine the extent to which different cognitive factors can predict the blood oxygenation level dependent (BOLD) response to targets. Our results reveal that both probability of positive identification (similarity to target) and proximity to the 50% decision boundary (ambiguity) are significant predictors of BOLD signal change, particularly in the right VLPFC. Furthermore, the profile of target related signal change is not static, with the degree of selectivity increasing as the task becomes familiar. These findings demonstrate that frontoparietal sub-regions are recruited under increased cognitive demand and that when recruited, they adapt, using both fast and slow mechanisms, to selectively respond to those items that are of the most relevance to current intentions.
Chamberlain SR, Menzies L, Hampshire A, et al., 2008, Orbitofrontal dysfunction in patients with obsessive-compulsive disorder and their unaffected relatives, Science, Vol: 321, Pages: 421-422, ISSN: 1095-9203
Obsessive-compulsive disorder (OCD) is characterized by repetitive thoughts and behaviors associated with underlying dysregulation of frontostriatal circuitry. Central to neurobiological models of OCD is the orbitofrontal cortex, a neural region that facilitates behavioral flexibility after negative feedback (reversal learning). We identified abnormally reduced activation of several cortical regions, including the lateral orbitofrontal cortex, during reversal learning in OCD patients and their clinically unaffected close relatives, supporting the existence of an underlying previously undiscovered endophenotype for this disorder.
Williams-Gray CH, Hampshire A, Robbins TW, et al., 2007, Catechol O-methyltransferase Val158Met genotype influences frontoparietal activity during planning in patients with Parkinson's disease, J Neurosci, Vol: 27, Pages: 4832-4838, ISSN: 1529-2401
Cognitive dysfunction commonly occurs even in the early stages of Parkinson's disease (PD). Impairment on frontostriatally based executive tasks is particularly well described but affects only a proportion of early PD patients. Our previous work suggests that a common functional polymorphism (val(158)met) within the catechol O-methyltransferase (COMT) gene underlies some of this executive heterogeneity. In particular, an increasing number of methionine alleles, resulting in lower enzyme activity, is associated with impaired performance on the "Tower of London" planning task. The main objective of this study was to investigate the underlying neural basis of this genotype-phenotype effect in PD using functional magnetic resonance imaging. We scanned 31 patients with early PD who were homozygous for either valine (val) (n = 16) or methionine (met) (n = 15) at the COMT val(158)met polymorphism during performance of an executive task comprising both Tower of London (planning) and simple subtracting ("control") problems. A cross-group comparison between genetic subgroups revealed that response times for planning problems were significantly longer in met compared with val homozygotes, whereas response times for control problems did not differ. Furthermore, imaging data revealed a significant reduction in blood oxygen level-dependent signal across the frontoparietal network involved in planning in met/met compared with val/val patients. Hence, we have demonstrated that COMT genotype impacts on executive function in PD through directly influencing frontoparietal activation. Furthermore, the directionality of the genotype-phenotype effect observed in this study, when interpreted in the context of the existing literature, adds weight to the hypothesis that the relationship between prefrontal function and dopamine levels follows as an inverted U-shaped curve.
Boly M, Coleman MR, Davis MH, et al., 2007, When thoughts become action: an fMRI paradigm to study volitional brain activity in non-communicative brain injured patients, Neuroimage, Vol: 36, Pages: 979-992, ISSN: 1053-8119
The assessment of voluntary behavior in non-communicative brain injured patients is often challenging due to the existence of profound motor impairment. In the absence of a full understanding of the neural correlates of consciousness, even a normal activation in response to passive sensory stimulation cannot be considered as proof of the presence of awareness in these patients. In contrast, predicted activation in response to the instruction to perform a mental imagery task would provide evidence of voluntary task-dependent brain activity, and hence of consciousness, in non-communicative patients. However, no data yet exist to indicate which imagery instructions would yield reliable single subject activation. The aim of the present study was to establish such a paradigm in healthy volunteers. Two exploratory experiments evaluated the reproducibility of individual brain activation elicited by four distinct mental imagery tasks. The two most robust mental imagery tasks were found to be spatial navigation and motor imagery. In a third experiment, where these two tasks were directly compared, differentiation of each task from one another and from rest periods was assessed blindly using a priori criteria and was correct for every volunteer. The spatial navigation and motor imagery tasks described here permit the identification of volitional brain activation at the single subject level, without a motor response. Volunteer as well as patient data [Owen, A.M., Coleman, M.R., Boly, M., Davis, M.H., Laureys, S., Pickard J.D., 2006. Detecting awareness in the vegetative state. Science 313, 1402] strongly suggest that this paradigm may provide a method for assessing the presence of volitional brain activity, and thus of consciousness, in non-communicative brain-injured patients.
Hampshire A, Duncan J, Owen AM, 2007, Selective tuning of the blood oxygenation level-dependent response during simple target detection dissociates human frontoparietal subregions, J Neurosci, Vol: 27, Pages: 6219-6223, ISSN: 1529-2401
Current models of working memory and focal attention converge on the idea of an adaptable global system, distributed across a network of frontal and parietal brain regions. Here, we examine how the human frontoparietal network selectively adapts to represent currently relevant information during a simple attentional task: monitoring for a target item in a series of nontargets. Across the entire frontoparietal network, there is selective response to targets, in line with a global system for coding task-relevant inputs. At the same time, there are striking dissociations in response to nontargets; whereas ventrolateral frontal cortex responds just to the target, more dorsal/anterior regions respond to all stimuli from the target category. The results show different degrees of target selectivity across different regions of the frontoparietal network.
Hampshire A, Owen AM, 2006, Fractionating attentional control using event-related fMRI, Cereb Cortex, Vol: 16, Pages: 1679-1689, ISSN: 1047-3211
Despite numerous functional neuroimaging and lesion studies of human executive function, the precise neuroanatomical correlates of specific components of attentional control remain controversial. Using a novel approach that focused upon volunteer behavior rather than experimental manipulations, specific components of attentional shifting were fractionated, and their neural correlates differentiated using event-related fMRI. The results demonstrate that the ventrolateral prefrontal cortex is involved in switching attention "between" stimulus dimensions, whereas the posterior parietal cortex mediates changes in stimulus-response mapping. Furthermore, reversals based on negative feedback activated the lateral orbitofrontal cortex, whereas positive feedback modulated activity in the medial orbital frontal cortex. Finally, the dorsolateral prefrontal cortex was active throughout solution search. These findings support the hypothesis that lateral prefrontal, orbital, and parietal areas form a supervisory network that controls the focus of attention and suggests that these regions can be fractionated in terms of their specific contributions.
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