ORCID Profile
0000-0002-8301-033X
Current Organisation
University of Sydney
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Publisher: Elsevier BV
Date: 08-2016
DOI: 10.1016/J.NEUROSCIENCE.2016.05.029
Abstract: Verbal fluency refers to the ability to generate as many words as possible in a limited time interval, without repetition and according to either a phonologic (each word begins with a given letter) or a semantic rule (each word belongs to a given semantic category). While current literature suggests the involvement of left fronto-temporal structures in fluency tasks, whether the same or distinct brain areas are necessary for each type of fluency remains unclear. We tested the hypothesis for an involvement of partly segregated cortico-subcortical structures between phonologic and semantic fluency by examining with a voxel-based lesion symptom mapping approach the effects of brain lesions on fluency scores corrected for age and education level in a group of 191 unselected brain-damaged patients with a first left or right hemispheric lesion. There was a positive correlation between the scores to the two types of fluency, suggesting that common mechanisms underlie the word generation independent of the production rule. The lesion-symptom mapping revealed that lesions to left basal ganglia impaired both types of fluency and that left superior temporal, supramarginal and rolandic operculum lesions selectively impaired phonologic fluency and left middle temporal lesions impaired semantic fluency. Our results corroborate current neurocognitive models of word retrieval and production, and refine the role of cortical-subcortical interaction in lexical search by highlighting the common executive role of basal ganglia in both types of verbal fluency and the preferential involvement of the ventral and dorsal language pathway in semantic and phonologic fluency, respectively.
Publisher: Oxford University Press (OUP)
Date: 06-2020
DOI: 10.1093/SCAN/NSAA085
Abstract: Negative and positive emotions are known to shape decision-making toward more or less impulsive responses, respectively. Decision-making and emotion processing are underpinned by shared brain regions including the ventromedial prefrontal cortex (vmPFC) and the amygdala. How these processes interact at the behavioral and brain levels is still unclear. We used a lesion model to address this question. Study participants included in iduals diagnosed with behavioral-variant frontotemporal dementia (bvFTD, n = 18), who typically present deficits in decision-making/emotion processing and atrophy of the vmPFC, in iduals with Alzheimer’s disease (AD, n = 12) who present with atrophy in limbic structures and age-matched healthy controls (CTRL, n = 15). Prior to each choice on the delay discounting task participants were cued with a positive, negative or neutral picture and asked to vividly imagine witnessing the event. As hypothesized, our findings showed that bvFTD patients were more impulsive than AD patients and CTRL and did not show any emotion-related modulation of delay discounting rate. In contrast, AD patients showed increased impulsivity when primed by negative emotion. This increased impulsivity was associated with reduced integrity of bilateral amygdala in AD but not in bvFTD. Altogether, our results indicate that decision-making and emotion interact at the level of the amygdala supporting findings from animal studies.
Publisher: Elsevier BV
Date: 09-2018
DOI: 10.1016/J.CORTEX.2018.06.005
Abstract: Procedural memory refers to skills acquired through practice and depends on cortico-striatal and cortico-cerebellar circuits. These circuits are typically affected in Parkinson's disease (PD), leading to impaired skill learning, including defective offline consolidation, early in the course of the disease. Evidence points to a role of slow oscillations (<4 Hz) during sleep for offline consolidation. However recent studies showed consolidation over the course of the day, suggesting that consolidation may arise during wakefulness, too. Here we investigate whether functional connectivity (FC) at rest after visuo-motor skill learning is associated with the extent of offline improvements in healthy controls and PD patients. Nineteen participants (9 PD, 10 healthy controls) performed a mirror-drawing task. High-density 156-channel resting state EEG was recorded before and immediately after training. Performance on the task was measured again 24 h later to test for offline consolidation. Delta-band (1-3.5 Hz) FC centered on the left parietal cortex after training predicted offline consolidation. Weak FC was observed in most healthy controls and associated with marked overnight improvement, while strong FC was observed in most PD patients and associated with weak offline consolidation or loss of the skill. These findings indicate that offline consolidation starts immediately after visuo-motor skill learning in brain regions and frequencies typically involved in sleep-related consolidation.
Publisher: Elsevier BV
Date: 08-2018
DOI: 10.1016/J.NEUROIMAGE.2018.05.003
Abstract: Spontaneous brain activity at rest is highly organized even when the brain is not explicitly engaged in a task. Functional connectivity (FC) in the alpha frequency band (α, 8-12 Hz) during rest is associated with improved performance on various cognitive and motor tasks. In this study we explored how FC is associated with visuo-motor skill learning and offline consolidation. We tested two hypotheses by which resting-state FC might achieve its impact on behavior: preparing the brain for an upcoming task or consolidating training gains. Twenty-four healthy participants were assigned to one of two groups: The experimental group (n = 12) performed a computerized mirror-drawing task. The control group (n = 12) performed a similar task but with concordant cursor direction. High-density 156-channel resting-state EEG was recorded before and after learning. Subjects were tested for offline consolidation 24h later. The Experimental group improved during training and showed offline consolidation. Increased α-FC between the left superior parietal cortex and the rest of the brain before training and decreased α-FC in the same region after training predicted learning. Resting-state FC following training did not predict offline consolidation and none of these effects were present in controls. These findings indicate that resting-state alpha-band FC is primarily implicated in providing optimal neural resources for upcoming tasks.
Publisher: Korean Neurological Association
Date: 2018
Publisher: Elsevier BV
Date: 02-2019
DOI: 10.1016/J.SCHRES.2018.07.036
Abstract: A false sense of reality is a characteristic of schizophrenia spectrum disorders (SSD). Reality confusion may also emanate from posterior orbitofrontal cortex (OFC) lesions, as evident in confabulations that patients act upon and disorientation. This confusion can be measured by repeated runs of a continuous recognition task (CRT): patients increase their false positive rate from the second run on, failing to realize that an item is not a repetition within the current run. Correct handling of these stimuli, a faculty called orbitofrontal reality filtering (ORFi), induces a distinct frontal potential at 200-300 ms, the "ORFi potential". Patients with schizophrenia have been reported to fail in this task, too. Here, we explored the electrophysiology of ORFi in SSD. Evoked potentials, source, and connectivity analyses derived from high-density electroencephalograms of 17 patients with SSD and 15 age-matched healthy controls performing two runs of a CRT. Although the patients obtained normal performance, they did not normally express the frontal potential typical of ORFi between 200 and 300 ms. Coherence analysis demonstrated virtually absent functional connectivity in the theta band within the memory network in this period. Source analysis showed increased activity in left medial temporal and prefrontal regions in patients. SSD patients appear to invoke compensatory resources to handle the challenges of reality filtering. An abnormal ORFi potential may be an early biomarker of SSD.
Publisher: Elsevier BV
Date: 2019
Publisher: Elsevier BV
Date: 07-2016
DOI: 10.1016/J.CLINPH.2016.04.015
Abstract: Information learned in a spaced way is usually better recognized than information learned in a massed way. The brain mechanisms underlying this spacing effect remain unclear. We applied anodal transcranial direct current stimulation (tDCS) to the left and right prefrontal (PFC) or posterior parietal (PPC) cortices to study how stimulation influences learning and retrieval of information, as evidenced by item recognition and the spacing effect, and whether the effects are lateralized according to stimulus material and site of stimulation. We devised a continuous recognition task with verbal and non-verbal stimuli repeated either immediately or after a delay. Stimulus recognition was tested 30min later. There was a spacing effect for both materials, which, however, was not modulated by tDCS. Nonetheless, tDCS differentially impacted memory retrieval regardless of repetition mode during learning: tDCS over the PPC during learning enhanced recognition of non-verbal material regardless of side of stimulation, while tDCS over the left PFC decreased recognition regardless of material. The PPC seems to be involved specifically in the mnesic treatment of non-verbal material whereas the left PFC specifically influences learning irrespective of stimulus material. Prefrontal and posterior parietal cortices follow different lateralization rules in recognition memory.
Publisher: Elsevier BV
Date: 04-2013
Publisher: Frontiers Media SA
Date: 11-2017
Publisher: Elsevier BV
Date: 06-2016
DOI: 10.1016/J.NEUROPSYCHOLOGIA.2016.03.030
Abstract: Performance on paradigms involving switching between emotional and non-emotional task-sets (affective flexibility) predicts emotion regulation abilities and is impaired in patients with different emotional disorders. A better understanding of how neurostimulation techniques such as transcranial direct current stimulation (tDCS) influence affective switching may provide support for the improvement of rehabilitation programs. In the current study healthy volunteers received anodal tDCS over the right dorsolateral prefrontal cortex (DLPFC), the left DLPFC or sham stimulation while performing an affective-switching task. Participants had to repeat or switch between facial judgments of emotional expressions (emotional task-set) or gender (non-emotional task-set). Right tDCS resulted in faster responses in the gender task only when it followed a judgment of emotion. These effects were not observed following left tDCS. Further, switching away from emotion was easier for the right compared to left tDCS group (reduced switch costs for gender), while switching away from gender toward emotion was easier for the left compared to the right group (reduced switch-costs for emotion). In sum, tDCS over the DLPFC may modulate affective flexibility and right stimulation may be particularly helpful to facilitate disengagement from emotional task-sets. The usefulness of tDCS-trained affective switching may be further investigated on larger therapeutic protocols targeting emotional disorders.
Publisher: MIT Press - Journals
Date: 06-2012
DOI: 10.1162/JOCN_A_00150
Abstract: Optimal behavior relies on flexible adaptation to environmental requirements, notably based on the detection of errors. The impact of error detection on subsequent behavior typically manifests as a slowing down of RTs following errors. Precisely how errors impact the processing of subsequent stimuli and in turn shape behavior remains unresolved. To address these questions, we used an auditory spatial go/no-go task where continual feedback informed participants of whether they were too slow. We contrasted auditory-evoked potentials to left-lateralized go and right no-go stimuli as a function of performance on the preceding go stimuli, generating a 2 × 2 design with “preceding performance” (fast hit [FH], slow hit [SH]) and stimulus type (go, no-go) as within-subject factors. SH trials yielded SH trials on the following trials more often than did FHs, supporting our assumption that SHs engaged effects similar to errors. Electrophysiologically, auditory-evoked potentials modulated topographically as a function of preceding performance 80–110 msec poststimulus onset and then as a function of stimulus type at 110–140 msec, indicative of changes in the underlying brain networks. Source estimations revealed a stronger activity of prefrontal regions to stimuli after successful than error trials, followed by a stronger response of parietal areas to the no-go than go stimuli. We interpret these results in terms of a shift from a fast automatic to a slow controlled form of inhibitory control induced by the detection of errors, manifesting during low-level integration of task-relevant features of subsequent stimuli, which in turn influences response speed.
Publisher: Wiley
Date: 12-07-2019
DOI: 10.1002/HIPO.23137
Abstract: The mediotemporal lobe (MTL), including the hippoc us, is involved in all stages of episodic memory including memory encoding, consolidation, and retrieval. However, the exact timing of the hippoc us' involvement immediately after stimulus encounter remains unclear. In this study, we used high-density 156-channel electroencephalography to study the processing of entirely new stimuli, which had to be encoded, in comparison to highly overlearned stimuli. Sixteen healthy subjects performed a continuous recognition task with meaningful pictures repeated up to four consecutive times. Waveform and topographic cluster analyses of event-related potentials revealed that new items, in comparison to repetitions, were processed significantly differently at 220-300 ms. Source estimation localized activation for processing new stimuli in the right MTL. Our study demonstrates the occurrence of a transient signal from the MTL in response to new information already at 200-300 ms poststimulus onset, which presumably reflects encoding as an initial step toward memory consolidation.
Publisher: Oxford University Press (OUP)
Date: 17-09-2012
Abstract: Pantomimes of object use require accurate representations of movements and a selection of the most task-relevant gestures. Prominent models of praxis, corroborated by functional neuroimaging studies, predict a critical role for left parietal cortices in pantomime and advance that these areas store representations of tool use. In contrast, lesion data points to the involvement of left inferior frontal areas, suggesting that defective selection of movement features is the cause of pantomime errors. We conducted a large-scale voxel-based lesion-symptom mapping analyses with configural/spatial (CS) and body-part-as-object (BPO) pantomime errors of 150 left and right brain-damaged patients. Our results confirm the left hemisphere dominance in pantomime. Both types of error were associated with damage to left inferior frontal regions in tumor and stroke patients. While CS pantomime errors were associated with left temporoparietal lesions in both stroke and tumor patients, these errors appeared less associated with parietal areas in stroke than in tumor patients and less associated with temporal in tumor than stroke patients. BPO errors were associated with left inferior frontal lesions in both tumor and stroke patients. Collectively, our results reveal a left intrahemispheric dissociation for various aspects of pantomime, but with an unspecific role for inferior frontal regions.
Publisher: Wiley
Date: 09-12-2018
DOI: 10.1002/HIPO.23053
Abstract: Immediately repeated meaningful pictures in a continuous recognition task induce a positive frontal potential at about 200-300 ms, which appears to emanate from the medial temporal lobe (MTL) centered on the hippoc us, as concluded from inverse solutions, coherence measurements, and depth electrode recordings in humans. In this study, we tested patients with unilateral MTL lesions due to stroke to verify the provenance of this signal and its association with the spacing effect (SE)-the improved learning of material encountered in spaced rather than massed presentation. We found that unilateral left or right MTL lesions abolished the early frontal MTL-mediated signal but not the spacing effect. We conclude that the SE does not depend on MTL integrity. We suggest that the early frontal signal at 200-300 ms after immediate picture repetition may serve as a direct biomarker of MTL integrity that may be useful in the early stages of diseases like Alzheimer's.
Publisher: Wiley
Date: 09-12-2016
DOI: 10.1111/EJN.13114
Abstract: Stimuli are better retained in memory if they are repeated after a delay than if they are immediately repeated. This effect is called the spacing effect (SE). Recent electroencephalographic (EEG) studies showed that delayed repetition of meaningful designs in a continuous recognition task induces an evoked response very similar to new presentations. In contrast, immediately repeated designs induced circumscribed, stronger activation of the left medio-temporal lobe (MTL) at 200-300 ms. In amnesic subjects, this signal was missing, indicating that it has a memory-protective effect. Here, high-density EEG was used in humans to explore whether meaningless verbal (non-words) and non-verbal (geometric designs) stimuli also have a SE associated with such lateralized, temporally limited activation of the left MTL upon immediate repetition. The results revealed a SE for both materials. Timing and localization of brain activity differed as a function of stimulus material. Specific responses to immediate repetitions occurred at 200-285 ms for non-verbal stimuli and at 285-380 ms for verbal material. Source estimations revealed increased activity in right inferior frontal areas for immediate non-verbal repetitions and in left fronto-parietal areas for immediate verbal repetition in comparison to new presentations. These findings show that, while the SE is a ubiquitous phenomenon, the neural processes underlying it vary according to stimulus material.
Publisher: Elsevier BV
Date: 11-2014
DOI: 10.1016/J.NEUROIMAGE.2014.06.059
Abstract: A current controversy surrounds the question whether high-level features of a stimulus such as its relevance to the current task may affect early attentional processes. According to one view abruptly appearing stimuli gain priority during an initial feedforward processing stage and therefore capture attention even if they are irrelevant to the task. Alternatively, only stimuli that share a relevant property with the target may capture attention of the observer. Here, we used high-density EEG to test whether task relevance may modulate early feedforward brain activity, or whether it only becomes effective once the physical characteristics of the stimulus have been processed. We manipulated task relevance and visual saliency of distracters presented left or right of an upcoming central target. We found that only the relevance of distracters had an effect on manual reaction times to the target. However, the analysis of electrocortical activity revealed three discrete processing stages during which pure effects of distracter saliency (~80-160 ms), followed by an interaction between saliency and relevance (~130-240 ms) and finally pure effects of relevance (~230-370 ms) were observed. Electrical sources of early saliency effects and later relevance effects were localized in the posterior parietal cortex, predominantly over the right hemisphere. These findings support the view that during the initial feedforward stage only physical (bottom-up) factors determine cortical responses to visual stimuli, while top-down effects interfere at later processing stages.
Publisher: Springer Science and Business Media LLC
Date: 10-12-2019
DOI: 10.1038/S41598-019-55157-Z
Abstract: Delay discounting requires computing trade-offs between immediate-small rewards and later-larger rewards. Negative and positive emotions shift decisions towards more or less impulsive responses, respectively. Models have conceptualized this trade-off by describing an interplay between “emotional” and “rational” processes, with the former involved during immediate choices and relying on the ventromedial prefrontal cortex (vmPFC), and the latter involved in long-term choices and relying on the dorsolateral prefrontal cortex (dlPFC). Whether stimulation of the vmPFC modulates emotion-induced delay discounting remains unclear. We applied tDCS over the vmPFC in 20 healthy in iduals during a delay discounting task following an emotional (positive, negative) or neutral induction. Our results showed that cathodal tDCS increased impulsivity after positive emotions in high impulsivity trials. For low impulsivity trials, anodal tDCS decreased impulsivity following neutral induction compared with emotional induction. Our findings demonstrate that the vmPFC integrates reward and emotion most prominently in situations of increased impulsivity, whereas when higher cognitive control is required the vmPFC appears to be less engaged, possibly due to recruitment of the dlPFC. Understanding how stimulation and emotion influence decision-making at the behavioural and neural levels holds promise to develop interventions to reduce impulsivity.
Publisher: Springer Science and Business Media LLC
Date: 05-03-2019
DOI: 10.1007/S00415-019-09261-9
Abstract: The objective of the study is to determine the utility of a simple reaction time task as a marker of general cognitive decline across the frontotemporal lobar degeneration (FTLD) spectrum and in Alzheimer's disease (AD). One hundred and twelve patients presenting with AD or FTLD affecting behaviour (behavioural-variant frontotemporal dementia), language (progressive non fluent aphasia, logopenic progressive aphasia, semantic dementia) or motor function (corticobasal syndrome, progressive supranuclear palsy, frontotemporal dementia-motor neuron disease) and 25 age-matched healthy controls completed the Psychomotor Vigilance Task (PVT), a 3-min reaction time (RT) task. The proportion of lapses (RT > 500 ms) was significantly increased in dementia patients compared to healthy controls, except for semantic dementia, and correlated with all cognitive functions except language. Discrimination of in iduals (dementia patients versus healthy controls) based on the proportion of lapses yielded the highest classification performance (Area Under the Curve, AUC, 0.90) compared to standard neuropsychological tests. Only the complete and lengthy neuropsychological battery had a higher predictive value (AUC 0.96). The basic ability to sustain attention is fundamental to perform any cognitive task. Lapses, interpreted as momentary shifts in goal-directed processing, can therefore, be used as a marker of general cognitive decline indicative of possible dementia.
Publisher: Society for Neuroscience
Date: 13-10-2010
DOI: 10.1523/JNEUROSCI.2064-10.2010
Abstract: Inhibitory control, a core component of executive functions, refers to our ability to suppress intended or ongoing cognitive or motor processes. Mostly based on Go/NoGo paradigms, a considerable amount of literature reports that inhibitory control of responses to “NoGo” stimuli is mediated by top-down mechanisms manifesting ∼200 ms after stimulus onset within frontoparietal networks. However, whether inhibitory functions in humans can be trained and the supporting neurophysiological mechanisms remain unresolved. We addressed these issues by contrasting auditory evoked potentials (AEPs) to left-lateralized “Go” and right NoGo stimuli recorded at the beginning versus the end of 30 min of active auditory spatial Go/NoGo training, as well as during passive listening of the same stimuli before versus after the training session, generating two separate 2 × 2 within-subject designs. Training improved Go/NoGo proficiency. Response times to Go stimuli decreased. During active training, AEPs to NoGo, but not Go, stimuli modulated topographically with training 61–104 ms after stimulus onset, indicative of changes in the underlying brain network. Source estimations revealed that this modulation followed from decreased activity within left parietal cortices, which in turn predicted the extent of behavioral improvement. During passive listening, in contrast, effects were limited to topographic modulations of AEPs in response to Go stimuli over the 31–81 ms interval, mediated by decreased right anterior temporoparietal activity. We discuss our results in terms of the development of an automatic and bottom-up form of inhibitory control with training and a differential effect of Go/NoGo training during active executive control versus passive listening conditions.
Publisher: Frontiers Media SA
Date: 2013
Publisher: Elsevier BV
Date: 11-2020
Publisher: Elsevier BV
Date: 02-2011
DOI: 10.1016/J.IJPSYCHO.2010.10.017
Abstract: Both neural and behavioral responses to stimuli are influenced by the state of the brain immediately preceding their presentation, notably by pre-stimulus oscillatory activity. Using frequency analysis of high-density electroencephalogram coupled with source estimations, the present study investigated the role of pre-stimulus oscillatory activity in auditory spatial temporal order judgments (TOJ). Oscillations within the beta range (i.e. 18-23 Hz) were significantly stronger before accurate than inaccurate TOJ trials. Distributed source estimations identified bilateral posterior sylvian regions as the principal contributors to pre-stimulus beta oscillations. Activity within the left posterior sylvian region was significantly stronger before accurate than inaccurate TOJ trials. We discuss our results in terms of a modulation of sensory gating mechanisms mediated by beta activity.
Publisher: Elsevier BV
Date: 04-2014
DOI: 10.1016/J.NEUROSCIENCE.2014.01.052
Abstract: Orbitofrontal reality filtering denotes a memory control mechanism necessary to keep thought and behavior in phase with reality. Its failure induces reality confusion as evident in confabulation and disorientation. In the present study, we explored the influence of orbitofrontal transcranial direct current stimulation (tDCS) on reality filtering. Twenty healthy human subjects made a reality filtering task, while receiving cathodal, anodal, or sham stimulation over the frontal pole in three sessions separated by at least 1week. Computational models predicted that this montage can produce polarity-specific current flow across the posterior medial orbitofrontal cortex (OFC). In agreement with our hypothesis, we found that cathodal tDCS over the frontal pole specifically impaired reality filtering in comparison to anodal and sham stimulation. This study shows that reality filtering, an orbitofrontal function, can be modulated with tDCS.
Publisher: Elsevier BV
Date: 03-2015
DOI: 10.1016/J.NEUROSCIENCE.2014.12.064
Abstract: Orbitofrontal reality filtering (ORF) denotes a little known but vital memory control mechanism, expressed at 200-300ms after stimulus presentation, that allows one to sense whether evoked memories (thoughts) refer to present reality and can be acted upon, or not. Its failure induces reality confusion evident in confabulations that patients act upon and disorientation. In what way ORF differs from temporal order judgment (TOJ), that is, the conscious knowledge about when something happened in the past, has never been explored. Here we used evoked potential analysis to compare ORF and TOJ within a combined experimental task and within a comparable time frame, close to the experienced present. Seventeen healthy human subjects performed an experiment using continuous recognition tasks that combined the challenges of ORF and TOJ. We found that the two mechanisms dissociated behaviorally: subjects were markedly slower and less accurate in TOJ than ORF. Both mechanisms evoked similar potentials at 240-280ms, when ORF normally occurs. However, they rapidly dissociated in terms of litude differences and electrical source from 310 to 360ms and again from 530 to 560ms. We conclude that the task of consciously ordering memories in the immediate past (TOJ) is effortful and slow in contrast to sensing memories' relation with the present (ORF). Both functions invoke similar early electrocortical processes which then rapidly dissociate and engage different brain areas. The results are consistent with the different consequences of the two mechanisms' dysfunction: while failure of ORF has a known clinical manifestation (reality confusion as evident in confabulation and disorientation), the failure of TOJ, as tested here, has no such known clinical correlate.
Publisher: Frontiers Media SA
Date: 2013
Publisher: Frontiers Media SA
Date: 31-05-2016
Publisher: Elsevier BV
Date: 11-2013
Publisher: Society for Neuroscience
Date: 07-12-2011
DOI: 10.1523/JNEUROSCI.3715-11.2011
Abstract: Behavioral and brain responses to identical stimuli can vary with experimental and task parameters, including the context of stimulus presentation or attention. More surprisingly, computational models suggest that noise-related random fluctuations in brain responses to stimuli would alone be sufficient to engender perceptual differences between physically identical stimuli. In two experiments combining psychophysics and EEG in healthy humans, we investigated brain mechanisms whereby identical stimuli are (erroneously) perceived as different (higher vs lower in pitch or longer vs shorter in duration) in the absence of any change in the experimental context. Even though, as expected, participants' percepts to identical stimuli varied randomly, a classification algorithm based on a mixture of Gaussians model (GMM) showed that there was sufficient information in single-trial EEG to reliably predict participants' judgments of the stimulus dimension. By contrasting electrical neuroimaging analyses of auditory evoked potentials (AEPs) to the identical stimuli as a function of participants' percepts, we identified the precise timing and neural correlates (strength vs topographic modulations) as well as intracranial sources of these erroneous perceptions. In both experiments, AEP differences first occurred ∼100 ms after stimulus onset and were the result of topographic modulations following from changes in the configuration of active brain networks. Source estimations localized the origin of variations in perceived pitch of identical stimuli within right temporal and left frontal areas and of variations in perceived duration within right temporoparietal areas. We discuss our results in terms of providing neurophysiologic evidence for the contribution of random fluctuations in brain activity to conscious perception.
Publisher: Elsevier BV
Date: 2011
DOI: 10.1016/J.NEUROPSYCHOLOGIA.2010.11.004
Abstract: An accurate sense of time contributes to functions ranging from the perception and anticipation of sensory events to the production of coordinated movements. However, accumulating evidence demonstrates that time perception is subject to strong illusory distortion. In two experiments, we investigated whether the subjective speed of temporal perception is dependent on our visual environment. By presenting human observers with speed-altered movies of a crowded street scene, we modulated performance on subsequent production of "20s" elapsed intervals. Our results indicate that one's visual environment significantly contributes to calibrating our sense of time, independently of any modulation of arousal. This plasticity generates an assay for the integrity of our sense of time and its rehabilitation in clinical pathologies.
Publisher: Informa UK Limited
Date: 18-12-2015
DOI: 10.1080/09297049.2015.1120861
Abstract: Orbitofrontal reality filtering denotes a memory control mechanism necessary to keep thought and behavior in phase with reality. In adults, it is mediated by the orbitofrontal cortex and subcortical connections and its failure induces reality confusion, confabulations, and disorientation. Here we investigated for the first time the development of this mechanism in 83 children from ages 7 to 11 years and 20 adults. We used an adapted version of a continuous recognition task composed of two runs with the same picture set but arranged in different order. The first run measures storage and recognition capacity (item memory), the second run measures reality filtering. We found that accuracy and reaction times in response to all stimulus types of the task improved in parallel across ages. Importantly, at no age was there a notable performance drop in the second run. This means that reality filtering was already efficacious at age 7 and then steadily improved as item memory became stronger. At the age of 11 years, reality filtering dissociated from item memory, similar to the pattern observed in adults. However, performance in 11-year-olds was still inferior as compared to adults. The study shows that reality filtering develops early in childhood and becomes more efficacious as memory capacity increases. For the time being, it remains unresolved, however, whether this function already depends on the orbitofrontal cortex, as it does in adults, or on different brain structures in the developing brains of children.
No related grants have been discovered for Aurelie Manuel.