Event-related alpha oscillations in task processing

Objectives: Recent findings substantiate the view that electroencephalograp hic (EEG) alpha rhythm (7-13 Hz) is functionally involved in information pr ocessing. However, the association of alpha rhythms with cognitive brain pr ocesses is less well understood because both augmentation and suppression o f alpha oscillations have been observed to accompany task performance. The present study evaluates the effect of task processing on event-related alph a oscillations at the level of single-sweep analysis. Methods: EEG was recorded from Fz, Cz and Pz electrodes in 10 subjects part icipating in two experimental sessions, in which auditory stimuli with equa l physical parameters were presented under different instructions (passive and task). Separate measurements of single-sweep amplitude and phase-lockin g were performed and statistically analyzed for consecutive time windows in the poststimulus epoch. Results: Major results show that, during the cognitive task, the phase-lock ing of alpha oscillations at the frontal site is significantly increased fo r the time window of 500-1000 ms after stimulation. Conclusions: The involvement of enhanced and synchronized frontal alpha act ivity in higher brain processes is strongly emphasized. (C) 1999 Elsevier S cience Ireland Ltd. All rights reserved.