The functional significance of event-related desynchronization of alpha rhythm in attentional and activating tasks.

The functional significance of event-related desynchronization (ERD) of alpha rhythm was investigated in a task which manipulated cognitive load and event rate. It was found that with increasing cognitive load the amount and duration of ERD increased. When a slow event rate was used the mean relative desynchronization of alpha rhythm and duration of ERD increased. These effects were found to be independent of one another. These results were interpreted as indicating that the mean ERD of alpha rhythm is sensitive to the selective attention demands of a task and the surprise value of stimuli.