AUDITORY-EVOKED RESPONSES INFLUENCED BY PRESENCE OR ABSENCE OF EEG ALPHA-ACTIVITY AND ACTUAL COGNITIVE STATE

The presence or absence of alpha activity in occipital EEG was detecte d automatically. Auditory-evoked responses (AERs) related to these two brain states and at the same time to different perceptual-cognitive s ituations (passive listening, discrimination between two tones and pre ssing the button accordingly similar discrimination without motor reac tion) were analyzed and compared statistically. The main result was th at during the alpha state (and not during the non-alpha state, when EE G was desynchronized), the amplitudes of N1, Pl waves and peak-to-peak amplitudes Nl-P2 were higher during passive listening to stimuli in c omparison with the active perceptual-cognitive states mentioned. No di fferences in latencies of AERs were found.