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Source Localization Analyses (source + localization_analysis)

Distribution by Scientific Domains

Psychology	50%

Selected Abstracts

Attentional load modifies early activity in human primary visual cortex

HUMAN BRAIN MAPPING, Issue 5 2009
Karsten S. Rauss
Abstract Recent theories of selective attention assume that the more attention is required by a task, the earlier are irrelevant stimuli filtered during perceptual processing. Previous functional MRI studies have demonstrated that primary visual cortex (V1) activation by peripheral distractors is reduced by higher task difficulty at fixation, but it remains unknown whether such changes affect initial processing in V1 or subsequent feedback. Here we manipulated attentional load at fixation while recording peripheral visual responses with high-density EEG in 28 healthy volunteers, which allowed us to track the exact time course of attention-related effects on V1. Our results show a modulation of the earliest component of the visual evoked potential (C1) as a function of attentional load. Additional topographic and source localization analyses corroborated this finding, with significant load-related differences observed throughout the first 100 ms post-stimulus. However, this effect was observed only when stimuli were presented in the upper visual field (VF), but not for symmetrical positions in the lower VF. Our findings demonstrate early filtering of irrelevant information under increased attentional demands, thus supporting models that assume a flexible mechanism of attentional selection, but reveal important functional asymmetries across the VF. Hum Brain Mapp 2009. © 2008 Wiley-Liss, Inc. [source]

Increased error-related negativity (ERN) in childhood anxiety disorders: ERP and source localization

THE JOURNAL OF CHILD PSYCHOLOGY AND PSYCHIATRY AND ALLIED DISCIPLINES, Issue 10 2006
Cecile D. Ladouceur
Background:, In this study we used event-related potentials (ERPs) and source localization analyses to track the time course of neural activity underlying response monitoring in children diagnosed with an anxiety disorder compared to age-matched low-risk normal controls. Methods:, High-density ERPs were examined following errors on a flanker task from 12 children between 8 and 14 years old diagnosed with an anxiety disorder (ANX) and 13 age-matched low-risk normal controls (LRNC). Results:, Children diagnosed with an anxiety disorder had increased error-related negativity (ERN) amplitude. The neural generators of the ERN in the ANX group were estimated to be localized in the anterior cingulate cortex (ACC). There were no significant group differences in PE amplitude. Conclusions:, These data provide evidence for increased ERN amplitude localized to the ACC in children diagnosed with an anxiety disorder, suggesting altered maturational patterns of the ACC circuitry early in the course of this illness. [source]

Magnetoencephalographic gamma power reduction in patients with schizophrenia during resting condition

HUMAN BRAIN MAPPING, Issue 10 2009
Lindsay Rutter
Abstract Objective: The "default network" represents a baseline condition of brain function and is of interest in schizophrenia research because its component brain regions are believed to be aberrant in the disorder. We hypothesized that magnetoencephalographic (MEG) source localization analysis would reveal abnormal resting activity within particular frequency bands in schizophrenia. Experimental Design: Eyes-closed resting state MEG signals were collected for two comparison groups. Patients with schizophrenia (N = 38) were age-gender matched with healthy control subjects (N = 38), and with a group of unmedicated unaffected siblings of patients with schizophrenia (N = 38). To localize 3D-brain regional differences, synthetic aperture magnetometry was calculated across established frequency bands as follows: delta (0.9,4 Hz), theta (4,8 Hz), alpha (8,14 Hz), beta (14,30 Hz), gamma (30,80 Hz), and super-gamma (80,150 Hz). Principle Observations: Patients with schizophrenia showed significantly reduced activation in the gamma frequency band in the posterior region of the medial parietal cortex. As a group, unaffected siblings of schizophrenia patients also showed significantly reduced activation in the gamma bandwidth across similar brain regions. Moreover, using the significant region for the patients and examining the gamma band power gave an odds ratio of 6:1 for reductions of two standard deviations from the mean. This suggests that the measure might be the basis of an intermediate phenotype. Conclusions: MEG resting state analysis adds to the evidence that schizophrenic patients experience this condition very differently than healthy controls. Whether this baseline difference relates to network abnormalities remains to be seen. Hum Brain Mapp, 2009. © 2009 Wiley-Liss, Inc. [source]

Distraction produces an increase in pain-evoked anterior cingulate activity

PSYCHOPHYSIOLOGY, Issue 4 2004
Robert Dowman
Abstract This study examined the effects of distraction on pain-evoked activity in the anterior cingulate cortex (ACC). Twenty-eight healthy adults were given painful electrical stimulation of the sural nerve during an attend condition, where they rated the subjective magnitude of each electrical stimulus, and during a distraction condition, where they performed an arithmetic distraction task. The magnitude of the pain-evoked ACC activity was estimated from the dipole source localization analysis of the somatosensory evoked potential. Subjective pain ratings were smaller and pain-evoked ACC activity was larger during the distraction condition than during the attend condition. Recent regional cerebral blood flow studies have also reported a distraction-related increase in pain-evoked ACC activity. Our results confirm these reports, and verify that the distraction effect specifically involves pain-evoked ACC activity. The cognitive demands of the distraction task present the possibility that the pain-evoked ACC activity might be involved, at least in part, in response competition and/or orienting attention toward painful stimuli. [source]