title: Functional topography during a visuoverbal judgment task studied with event-related desynchronization mapping.
abstract: Event-related desynchronization (ERD) of alpha components was studied in 10 subjects in a visuoverbal judgment task. EEG was recorded from 29 electrodes; ERD, measured by percentage of alpha power decrease, was calculated in 125-ms intervals and displayed in a time course over 7-s intervals and in the form of topographical ERD maps. ERD, interpreted as a measure of activated cortical areas, was studied in the upper and lower alpha bands. It was found that upper alpha band ERD was short-lasting (less than 1 s), localized to the posterior region and not found before stimulation; in contrast to this, lower alpha band ERD was longer-lasting (greater than 1 s), more widespread, with a left hemisphere dominance, and was already present before stimulation. ANOVA revealed significant interactions among alpha frequency bands, scalp location, and pre-/poststimulus intervals. The self-organizing topological Kohonen network was used to analyze the stability of consecutive ERD maps. There is evidence that topographical ERD patterns can be stable for about 300-400 ms.
authors.affiliation: Ludwig Boltzmann-Institute of Medical Informatics, Graz University of Technology, Austria.
authors.forename: G
authors.initials: G
authors.lastname: Pfurtscheller
authors.forename: W
authors.initials: W
authors.lastname: Klimesch
mesh_terms: D000328:Adult; D000818:Animals; D001143:Arousal / Q000502:physiology; D001931:Brain Mapping / Q000295:instrumentation*; D002540:Cerebral Cortex / Q000502:physiology*; D003344:Cortical Synchronization; D006224:Cricetinae; D004292:Dominance, Cerebral / Q000502:physiology*; D005074:Evoked Potentials, Visual / Q000502:physiology; D006801:Humans; D008297:Male; D009415:Nerve Net / Q000502:physiology; D011932:Reading; D012815:Signal Processing, Computer-Assisted / Q000295:instrumentation*; D014705:Verbal Behavior / Q000502:physiology*; D014796:Visual Perception / Q000502:physiology*