In JoVE (1)

Other Publications (55)

Articles by Sam Gilbert 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 Sam Gilbert on PubMed

Task Switching: a PDP Model

Cognitive Psychology. May, 2002  |  Pubmed ID: 11971634

When subjects switch between a pair of stimulus-response tasks, reaction time is slower on trial N if a different task was performed on trial N - 1. We present a parallel distributed processing (PDP) model that simulates this effect when subjects switch between word reading and color naming in response to Stroop stimuli. Reaction time on "switch trials" can be slowed by an extended response selection process which results from (a) persisting, inappropriate states of activation and inhibition of task-controlling representations; and (b) associative learning, which allows stimuli to evoke tasks sets with which they have recently been associated (as proposed by Allport & Wylie, 2000). The model provides a good fit to a large body of empirical data, including findings which have been seen as problematic for this explanation of switch costs, and shows similar behavior when the parameters are set to random values, supporting Allport and Wylie's proposal.

Vision: the Versatile 'visual' Cortex

Current Biology : CB. Dec, 2004  |  Pubmed ID: 15620640

The primary visual cortex is, of course, for vision--or so you would think. But it seems that, in blind people, the primary visual cortex can take on an important role in language processing. This suggests considerable flexibility in the processes by which subregions of the human brain become specialised for different functions.

Application of 2-D Free-flow Electrophoresis/RP-HPLC for Proteomic Analysis of Human Plasma Depleted of Multi High-abundance Proteins

Proteomics. Aug, 2005  |  Pubmed ID: 16052629

Free-flow electrophoresis (FFE) and rapid (6 min) RP-HPLC was used to fractionate human citrate-treated plasma. Prior to analysis, the six most abundant proteins in plasma were removed by immunoaffinity chromatography; both depleted plasma and the fraction containing the six abundant proteins depleted were taken for MS-based analysis. Fractionated proteins were digested with trypsin and the generated peptides were subjected to MS-based peptide sequencing. To date, 78 plasma proteins have been unambiguously identified by manual validation from 16% (15/96 FFE total fractions) of the collected FFE pools; 55 identifications were based on > or = 2 tryptic peptides and 23 using single peptides. The molecular weight range of proteins and peptides isolated by this method ranged from approximately 190 K (e.g., Complement C3 and C4) to approximately 4-6 K (e.g., CRISPP and Apolipoprotein C1). This FFE/RP-HPLC approach reveals low-abundance proteins and peptides (e.g., L-Selectin approximately 17 ng/mL and the cancer-associated SCM-recognition, immunodefense suppression, and serine protease protection peptide (CRISPP) at approximately 0.5-1 ng/mL), where CRISPP was found in association with alpha-1-antitrypsin as a non-covalent complex, in the fraction containing the depleted high-abundance proteins. In contrast to shotgun proteomic approaches, the FFE/RP-HPLC method described here allows the identification of potentially interesting peptides to be traced back to their protein of origin, and for the first time, has confirmed the "protein sponge" hypothesis where the 35 residue CRISPP polypeptide is non-covalently complexed with the major circulating plasma protein alpha-1-antitrypsin.

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.

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).

Does Task-set Reconfiguration Create Cognitive Slack?

Journal of Experimental Psychology. Human Perception and Performance. Feb, 2005  |  Pubmed ID: 15709865

C. Oriet and P. Jolicoeur (2003) reported 2 experiments in which the perceptual contrast of stimuli was manipulated in a task-switching paradigm. They failed to observe an interaction in the reaction time data between task switching, perceptual contrast, and response-stimulus interval. Using the locus of slack logic, they concluded from these results that early perceptual processing of stimuli awaits the completion of a task-set reconfiguration stage, rather than proceeding in parallel with it. Here, an assumption necessary for this argument is questioned, and it is shown that an existing computational model of task switching, without successive stages for task-set reconfiguration and perceptual processing, produces a similar pattern of data. Thus, C. Oriet and P. Jolicoeur's data are compatible with models in which early perceptual processing and task-set reconfiguration take place in parallel.

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.

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.

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.

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.

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 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.

Cognitive Functioning After Medial Frontal Lobe Damage Including the Anterior Cingulate Cortex: a Preliminary Investigation

Brain and Cognition. Mar, 2006  |  Pubmed ID: 16384629

Two patients with medial frontal lobe damage involving the anterior cingulate cortex (ACC) performed a range of cognitive tasks, including tests of executive function and anterior attention. Both patients lesions extended beyond the ACC, therefore caution needs to be exerted in ascribing observed deficits to the ACC alone. Patient performance was compared with age and education matched healthy controls. Both patients showed intact intellectual, memory, and language abilities. No clear-cut abnormalities were noted in visuoperceptual functions. Speed of information processing was mildly reduced only in Patient 2 (bilateral ACC lesion). The patients demonstrated weak or impaired performance only on selective executive function tests. Performance on anterior attention tasks was satisfactory. We tentatively suggest that our findings are inconsistent with anterior attention theories of ACC function based on neuroimaging findings. We propose that the data may imply that the ACC does not have a central role in cognition. We speculate that our findings may be compatible with the view that the ACC integrates cognitive processing with autonomic functioning to guide behaviour.

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.

Interim Cosmetic Results and Toxicity Using 3D Conformal External Beam Radiotherapy to Deliver Accelerated Partial Breast Irradiation in Patients with Early-stage Breast Cancer Treated with Breast-conserving Therapy

International Journal of Radiation Oncology, Biology, Physics. Nov, 2007  |  Pubmed ID: 17967306

We present our ongoing clinical experience utilizing three-dimensional (3D)-conformal radiation therapy (3D-CRT) to deliver accelerated partial breast irradiation (APBI) in patients with early-stage breast cancer treated with breast-conserving therapy.

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.

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.

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.

Reading Hidden Intentions in the Human Brain

Current Biology : CB. Feb, 2007  |  Pubmed ID: 17291759

When humans are engaged in goal-related processing, activity in prefrontal cortex is increased. However, it has remained unclear whether this prefrontal activity encodes a subject's current intention. Instead, increased levels of activity could reflect preparation of motor responses, holding in mind a set of potential choices, tracking the memory of previous responses, or general processes related to establishing a new task set. Here we study subjects who freely decided which of two tasks to perform and covertly held onto an intention during a variable delay. Only after this delay did they perform the chosen task and indicate which task they had prepared. We demonstrate that during the delay, it is possible to decode from activity in medial and lateral regions of prefrontal cortex which of two tasks the subjects were covertly intending to perform. This suggests that covert goals can be represented by distributed patterns of activity in the prefrontal cortex, thereby providing a potential neural substrate for prospective memory. During task execution, most information could be decoded from a more posterior region of prefrontal cortex, suggesting that different brain regions encode goals during task preparation and task execution. Decoding of intentions was most robust from the medial prefrontal cortex, which is consistent with a specific role of this region when subjects reflect on their own mental states.

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.

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.

Executive Function

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

Separable Forms of Reality Monitoring Supported by Anterior Prefrontal Cortex

Journal of Cognitive Neuroscience. Mar, 2008  |  Pubmed ID: 18004946

Reality monitoring refers to the process of discriminating between internally and externally generated information. Two different tasks have often been used to assess this ability: (a) memory for perceived versus imagined stimuli; and (b) memory for participant- versus experimenter-performed operations. However, it is not known whether these two reality monitoring tasks share neural substrates. The present study involved use of a within-subjects functional magnetic resonance imaging design to examine common and distinct brain mechanisms associated with the two reality monitoring conditions. The sole difference between the two lay in greater activation in the medial anterior prefrontal cortex when recollecting whether the participant or the experimenter had carried out an operation during prior encoding as compared to recollecting whether an item had been perceived or imagined. This region has previously been linked with attending to mental states. Task differences were also reflected in the nature of functional connectivity relationships between the medial anterior and right lateral prefrontal cortex: There was a stronger correlation in activity between the two regions during recollection of self/experimenter context. This indicates a role for the medial anterior prefrontal cortex in the monitoring of retrieved information relating to internal or external aspects of context. Finally, given the importance of reality monitoring to understanding psychotic symptoms, brain activity was related to measures of proneness to psychosis and schizotypal traits. The observation of significant correlations between reduced medial anterior prefrontal signal and scores on such measures corroborates these theoretical links.

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.

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.

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.

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.

Modification of Planned Actions

Experimental Brain Research. Jan, 2009  |  Pubmed ID: 18841355

To elucidate the time course and processes underlying pre-movement modification of planned actions, participants prepared to make an action at a time of their own choosing within a specified temporal window. In some conditions, participants prepared to make a single right index finger key press, whereas in others, they prepared to make a sequence of two key presses consisting of a right index finger key press followed by a right middle finger key press. On a proportion of trials, their internal preparation was interrupted by an auditory tone, in response to which they made either: the same action as they were intending, a different action requiring an additional effector (i.e. switch from preparing a single right index finger key press to executing a right index, middle finger sequence), or a different action requiring one less effector (i.e. switch from preparing a right index, middle finger sequence to executing a right index finger key press). For unmodified actions, switching from an internally generated to an externally triggered mode of response production produced a significant reaction time cost (RT cost) for both single and sequential actions, with the cost for single actions being significantly greater than that for sequential actions. Given that the RT cost did not increase as the complexity of the actions increased it is unlikely that the source of the cost is related to motor execution processes, and it is suggested that it may arise at a higher level cognitive stage of processing. In addition, reaction times to produce modified actions were significantly greater than those to produce unmodified actions. Finally, it took significantly longer to produce modified actions requiring one less effector than to produce modified actions requiring one more effector. We suggest that two time-consuming processes are involved in switching between internally generated and externally triggered actions that are modified or unmodified: a trigger switch cost when the same action has to be produced in response to an external trigger as opposed to an internal trigger, and a switch cost reflecting changes in the pattern of executed motor commands when modification is necessary. It is suggested that such processes may be mediated by regions of the frontal lobes.

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.

Development of the Selection and Manipulation of Self-generated Thoughts in Adolescence

The Journal of Neuroscience : the Official Journal of the Society for Neuroscience. Jun, 2010  |  Pubmed ID: 20519541

The ability to select and manipulate self-generated (stimulus-independent, SI), as opposed to stimulus-oriented (SO), information, in a controlled and flexible way has previously only been studied in adults. This ability is thought to rely in part on the rostrolateral prefrontal cortex (RLPFC), which continues to mature anatomically during adolescence. We investigated (1) the development of this ability behaviorally, (2) the associated functional brain development, and (3) the link between functional and structural maturation. Participants classified according to their shape letters either presented visually (SO phases) or that they generated in their head by continuing the alphabet sequence (SI phases). SI phases were performed in the presence or absence of distracting letters. A total of 179 participants (7-27 years old) took part in a behavioral study. Resistance to visual distractors exhibited small improvements with age. SI thoughts manipulation and switching between SI and SO thoughts showed steeper performance improvements extending into late adolescence. Thirty-seven participants (11-30 years old) took part in a functional MRI (fMRI) study. SI thought manipulation and switching between SO and SI thought were each associated with brain regions consistently recruited across age. A single frontal brain region in each contrast exhibited decreased activity with age: left inferior frontal gyrus/anterior insula for SI thought manipulation, and right superior RLPFC for switching between SO and SI thoughts. By integrating structural and functional data, we demonstrated that the observed functional changes with age were not purely consequences of structural maturation and thus may reflect the maturation of neurocognitive strategies.

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.

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.

The Scale of Functional Specialization Within Human Prefrontal Cortex

The Journal of Neuroscience : the Official Journal of the Society for Neuroscience. Jan, 2010  |  Pubmed ID: 20107051

At what scale is it possible to observe consistent functional specialization within human prefrontal cortex (PFC), reproducible from one individual to the next? Some studies suggest gross functional divisions between large regions of PFC, but it is not known whether PFC exhibits specialization at the fine-grained scale known to differentiate posterior cortical functions. We used fMRI to confirm a three-way segregation of function between three regions of medial anterior PFC, each centered on coordinates within 15 mm of the other two. Naive participants performed three tasks based on earlier studies, and we investigated activity at regions defined by previous results. In each task, signal was significantly greater at the predicted region than the other two, just millimeters away. These results indicate reproducible functional specialization within PFC, at a much finer scale than previously demonstrated. Furthermore, these findings suggest that divergent results from previous studies may reflect the recruitment of functionally distinct regions and that "reverse inference" should be undertaken with caution.

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.

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.

Involvement of Right Dorsolateral Prefrontal Cortex in Ill-structured Design Cognition: an FMRI Study

Brain Research. Feb, 2010  |  Pubmed ID: 19948156

In ill-structured tasks, the problem to be solved is poorly specified and there is no unique correct solution. Most evidence on brain mechanisms involved in dealing with such tasks comes from neuropsychology. Here, we developed an ill-structured design task suitable for testing in a functional neuroimaging environment and compared it with a matched well-structured problem-solving task using fMRI. Consistent with prior neuropsychological results, the design task was associated with greater activity in right dorsolateral prefrontal cortex compared with problem solving. This differential activity was specific to the problem studying phase rather than performance. Furthermore, the design and problem-solving tasks differed not only in overall levels of brain activity but also in patterns of functional interactions between brain regions. These results provide new evidence on the role of right dorsolateral prefrontal cortex in ill-structured situations, such as those involved in design cognition. Additionally, these results confirm the suitability of functional neuroimaging for studying such situations.

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.

Decoding the Content of Delayed Intentions

The Journal of Neuroscience : the Official Journal of the Society for Neuroscience. Feb, 2011  |  Pubmed ID: 21414910

Rostrolateral prefrontal cortex (RLPFC) plays a key role in our ability to postpone the execution of intended behaviors until after another activity has been performed. However, it is poorly understood in computational terms. One crucial question is whether RLPFC represents the content of delayed intentions or plays a nonspecific role. In this human functional magnetic resonance imaging study (n = 32), RLPFC was active while participants stored delayed intentions during a distracting ongoing task. Multivariate analysis showed that the intended cue for future action and the intended behavior could be decoded from distinct posterior brain regions. However, the content of intentions could not be decoded from RLPFC itself. Functional connectivity analysis showed that RLPFC increased its coupling with content-representing regions during intention storage. Furthermore, trials with relatively high RLPFC activity were associated with enhanced decoding. Thus, RLPFC may enable realization of delayed intentions via interactions with posterior brain regions, which represent their content.

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.

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.

Evaluative Vs. Trait Representation in Intergroup Social Judgments: Distinct Roles of Anterior Temporal Lobe and Prefrontal Cortex

Neuropsychologia. Dec, 2012  |  Pubmed ID: 22975194

When interacting with someone from another social group, one's responses may be influenced by both stereotypes and evaluations. Given behavioral results suggesting that stereotypes and evaluative associations operate independently, we used fMRI to test whether these biases are mediated by distinct brain systems. White participants viewed pairs of Black or White faces and judged them based on an evaluation (who would you befriend?) or a stereotype-relevant trait (who is more likely to enjoy athletic activities?). Multi-voxel pattern analysis revealed that a predominantly occipital network represented race in a context-invariant manner. However, lateral orbitofrontal cortex preferentially represented race during friendship judgments, whereas anterior medial prefrontal cortex preferentially represented race during trait judgments. Furthermore, representation of race in left temporal pole correlated with a behavioral measure of evaluative bias during friendship judgments and, independently, a measure of stereotyping during trait judgments. Whereas early sensory regions represent race in an apparently invariant manner, representations in higher-level regions are multi-componential and context-dependent.

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.

Training Social Cognition: from Imitation to Theory of Mind

Cognition. Feb, 2012  |  Pubmed ID: 22133627

Evidence for successful socio-cognitive training in typical adults is rare. This study attempted to improve Theory of Mind (ToM) and visual perspective taking in healthy adults by training participants to either imitate or to inhibit imitation. Twenty-four hours after training, all participants completed tests of ToM and visual perspective taking. The group trained to inhibit their tendency to imitate showed improved performance on the visual perspective-taking test, but not the ToM test. Neither imitation training, nor general inhibition training, had this effect. These results support a novel theory of social cognition suggesting that the same self-other discrimination process underlies imitation inhibition and perspective taking. Imitation, perspective taking and ToM are all pro-social processes--ways in which we reach out to others. Therefore, it is striking that perspective taking can be enhanced by suppressing imitation; to understand another, sometimes we need, not to get closer, but to pull away.

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.

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.

Similarity Between Brain Activity at Encoding and Retrieval Predicts Successful Realization of Delayed Intentions

Journal of Cognitive Neuroscience. Jan, 2012  |  Pubmed ID: 21736451

Remembering delayed intentions can be highly demanding. Accuracy in laboratory paradigms assessing prospective memory (PM) is typically well below ceiling, and failure to remember intended behaviors after a delay is a common occurrence in everyday life. However, relatively little is known of the potential differences in brain activity that distinguish successful versus unsuccessful PM. In this fMRI study, participants repeatedly encoded, stored, and then had the opportunity to retrieve intended behaviors while engaged in a distracting ongoing task. This yielded a success rate of approximately two thirds. Overall levels of brain activity distinguished successful versus unsuccessful trials at all three stages (encoding, storage, and retrieval), suggesting multiple neural determinants of PM success. In addition, the voxelwise similarity between patterns of brain activity at encoding and retrieval was greater for successful than unsuccessful trials. This was true even in posterior cingulate, which showed opposite patterns of signal change between encoding and retrieval. Thus, successful realization of delayed intentions may be associated with reinstatement of encoding context at the time of retrieval.

Automaticity and Control in Prospective Memory: a Computational Model

PloS One. 2013  |  Pubmed ID: 23555807

Prospective memory (PM) refers to our ability to realize delayed intentions. In event-based PM paradigms, participants must act on an intention when they detect the occurrence of a pre-established cue. Some theorists propose that in such paradigms PM responding can only occur when participants deliberately initiate processes for monitoring their environment for appropriate cues. Others propose that perceptual processing of PM cues can directly trigger PM responding in the absence of strategic monitoring, at least under some circumstances. In order to address this debate, we present a computational model implementing the latter account, using a parallel distributed processing (interactive activation) framework. In this model PM responses can be triggered directly as a result of spreading activation from units representing perceptual inputs. PM responding can also be promoted by top-down monitoring for PM targets. The model fits a wide variety of empirical findings from PM paradigms, including the effect of maintaining PM intentions on ongoing response time and the intention superiority effect. The model also makes novel predictions concerning the effect of stimulus degradation on PM performance, the shape of response time distributions on ongoing and prospective memory trials, and the effects of instructing participants to make PM responses instead of ongoing responses or alongside them. These predictions were confirmed in two empirical experiments. We therefore suggest that PM should be considered to result from the interplay between bottom-up triggering of PM responses by perceptual input, and top-down monitoring for appropriate cues. We also show how the model can be extended to simulate encoding new intentions and subsequently deactivating them, and consider links between the model's performance and results from neuroimaging.

Systematic Review: Are Overweight and Obese Individuals Impaired on Behavioural Tasks of Executive Functioning?

Neuropsychology Review. Jun, 2013  |  Pubmed ID: 23381140

This review was aimed at systematically investigating the evidence suggesting that obese individuals demonstrate impaired performance on behavioural tasks examining executive functioning abilities. A systematic review of literature was carried out by searching five separate databases (PsycINFO, MEDLINE, EMBASE, CINAHL and PubMed) and a hand search of relevant journals. Twenty-one empirical papers were identified from the search criteria and the results were considered in relation to different executive functioning domains. There is little consistency of results both within and across different domains of executive functioning. The review suggests that obese individuals show difficulties with decision-making, planning and problem-solving when compared to healthy weight controls, with fewer difficulties reported on tasks examining verbal fluency and learning and memory. A lack of replication and underreporting of descriptive data is a key limitation of studies in this area and further research is needed to examine the mechanisms underpinning the relationship between obesity and executive functioning.

The Neuropsychology of Starvation: Set-shifting and Central Coherence in a Fasted Nonclinical Sample

PloS One. 2014  |  Pubmed ID: 25338075

Recent research suggests certain neuropsychological deficits occur in anorexia nervosa (AN). The role of starvation in these deficits remains unclear. Studies of individuals without AN can elucidate our understanding of the effect of short-term starvation on neuropsychological performance.

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.

Autistic Adolescents Show Atypical Activation of the Brain's Mentalizing System Even Without a Prior History of Mentalizing Problems

Neuropsychologia. Apr, 2014  |  Pubmed ID: 24361475

Some autistic children pass classic Theory of Mind (ToM) tasks that others fail, but the significance of this finding is at present unclear. We identified two such groups of primary school age (labelled ToM+ and ToM-) and a matched comparison group of typically developing children (TD). Five years later we tested these participants again on a ToM test battery appropriate for adolescents and conducted an fMRI study with a story based ToM task. We also assessed autistic core symptoms at these two time points. At both times the ToM- group showed more severe social communication impairments than the ToM+ group, and while showing an improvement in mentalizing performance, they continued to show a significant impairment compared to the NT group. Two independent ROI analyses of the BOLD signal showed activation of the mentalizing network including medial prefrontal cortex, posterior cingulate and lateral temporal cortices. Strikingly, both ToM+ and ToM- groups showed very similar patterns of heightened activation in comparison with the NT group. No differences in other brain regions were apparent. Thus, autistic adolescents who do not have a history of mentalizing problems according to our ToM battery showed the same atypical neurophysiological response during mentalizing as children who did have such a history. This finding indicates that heterogeneity at the behavioural level may nevertheless map onto a similar phenotype at the neuro-cognitive level.

Solving the Detour Problem in Navigation: a Model of Prefrontal and Hippocampal Interactions

Frontiers in Human Neuroscience. 2015  |  Pubmed ID: 25852515

Adapting behavior to accommodate changes in the environment is an important function of the nervous system. A universal problem for motile animals is the discovery that a learned route is blocked and a detour is required. Given the substantial neuroscience research on spatial navigation and decision-making it is surprising that so little is known about how the brain solves the detour problem. Here we review the limited number of relevant functional neuroimaging, single unit recording and lesion studies. We find that while the prefrontal cortex (PFC) consistently responds to detours, the hippocampus does not. Recent evidence suggests the hippocampus tracks information about the future path distance to the goal. Based on this evidence we postulate a conceptual model in which: Lateral PFC provides a prediction error signal about the change in the path, frontopolar and superior PFC support the re-formulation of the route plan as a novel subgoal and the hippocampus simulates the new path. More data will be required to validate this model and understand (1) how the system processes the different options; and (2) deals with situations where a new path becomes available (i.e., shortcuts).

Strategic Use of Reminders: Influence of Both Domain-general and Task-specific Metacognitive Confidence, Independent of Objective Memory Ability

Consciousness and Cognition. May, 2015  |  Pubmed ID: 25666463

How do we decide whether to use external artifacts and reminders to remember delayed intentions, versus relying on unaided memory? Experiment 1 (N=400) showed that participants' choice to forgo reminders in an experimental task was independently predicted by subjective confidence and objective ability, even when the two measures were themselves uncorrelated. Use of reminders improved performance, explaining significant variance in intention fulfilment even after controlling for unaided ability. Experiment 2 (N=303) additionally investigated a pair of unrelated perceptual discrimination tasks, where the confidence and sensitivity of metacognitive judgments was decorrelated from objective performance using a staircase procedure. Participants with lower confidence in their perceptual judgments set more reminders in the delayed-intention task, even though confidence was unrelated to objective accuracy. However, memory confidence was a better predictor of reminder setting. Thus, propensity to set reminders was independently influenced by (a) domain-general metacognitive confidence; (b) task-specific confidence; and (c) objective ability.

Creating External Reminders for Delayed Intentions: Dissociable Influence on "task-positive" and "task-negative" Brain Networks

NeuroImage. Jan, 2015  |  Pubmed ID: 25451474

Studies of prospective memory and other paradigms requiring participants to remember delayed intentions typically reveal a distinction between lateral and medial rostral prefrontal cortex, whereby the experimental condition yields increased signal in the former region and decreased signal in the latter. These regions comprise nodes of larger "task-positive" and "task-negative" networks that often show opposite patterns of signal change in response to diverse cognitive demands. However, it is not clear to what extent activity in these networks is A) inverse but equivalent, or B) functionally dissociable. In order to address this question, participants performed an "intention-offloading" task while undergoing fMRI. On each trial they remembered a delayed intention, which they had the opportunity to fulfill after a brief filled delay. In one condition they were required to set an external reminder of this intention, while in the other they acted without any external memory aid. Results indicated a clear functional dissociation between the two networks. Compared with a control task with no delayed intention, there was a highly significant reduction in task-negative deactivation when participants used an external memory aid. However, there was no reduction in task-positive activation. These results are consistent with previous evidence that medial rostral prefrontal cortex plays a prominent role in representing the content of delayed intentions, accompanied by a reduction in BOLD signal and potentially increased theta-band oscillatory activity. This role is no longer required once an external reminder has been created. By contrast, lateral rostral prefrontal cortex may play a content-free role, unaffected by the offloading of content into the external environment.

Strategic Offloading of Delayed Intentions into the External Environment

Quarterly Journal of Experimental Psychology (2006). 2015  |  Pubmed ID: 25404057

In everyday life, we often use external artefacts such as diaries to help us remember intended behaviours. In addition, we commonly manipulate our environment, for example by placing reminders in noticeable places. Yet strategic offloading of intentions to the external environment is not typically permitted in laboratory tasks examining memory for delayed intentions. What factors influence our use of such strategies, and what behavioural consequences do they have? This article describes four online experiments (N = 1196) examining a novel web-based task in which participants hold intentions for brief periods, with the option to strategically externalize these intentions by creating a reminder. This task significantly predicted participants' fulfilment of a naturalistic intention embedded within their everyday activities up to one week later (with greater predictive ability than more traditional prospective memory tasks, albeit with weak effect size). Setting external reminders improved performance, and it was more prevalent in older adults. Furthermore, participants set reminders adaptively, based on (a) memory load, and (b) the likelihood of distraction. These results suggest the importance of metacognitive processes in triggering intention offloading, which can increase the probability that intentions are eventually fulfilled.

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