Reduction of EEG activity caused by a light flash.
Intertrial EP variance measured in response to a brief binocularly presented flash of light decreases with a time-course that overlaps the average EP. This decrease in variance is not exclusive to the alpha frequency band (8-12 c/sec) but it is selective for it. Subjects with large initial variance tend to show a large decrease in variance. There is no relationship between the magnitude of the decrease in variance and the consistency of the EP. The phenomenon reflected by the decrease in variance is probably identical with 'event-related desynchronization.' The results support the hypothesis that an EP may consist of two processes that overlap in time: a reduction in background EEG activity and an almost deterministic transient potential change.
D001921:Brain / Q000502:physiology*; D004569:Electroencephalography; D005071:Evoked Potentials; D006801:Humans; D010775:Photic Stimulation