Topographic mapping and habituation of event related EEG alpha band desynchronization.

Habituation of alpha wave suppression to an external auditory signal was studied using computer assisted EEG quantification procedures. Topographic maps of alpha amplitude were constructed from multiple electrode placements for seven healthy adults. The EEG preceding and following 10 standard or habituating stimuli, and 1 novel or sensitizing stimulus, was spectrally analyzed and stored as color amplitude maps. Individual and group composite maps were read-out and comparisons in alpha amplitude were made across stimulus conditions. The initial standard stimulus produced a sharp reduction in alpha amplitude whereas the 10th trial had no appreciable effect on spontaneous EEG activity. The novel stimulus immediately restored alpha desynchronization. The colormaps permitted easy visualization and quantification of the process of habituation and sensitization of the alpha rhythm.