Occipital rhythmic activity within the alpha band during conditioned externally paced movement.

The time-dependent behaviour of the power within the alpha band during conditioned movement was studied from the scalp EEG of 9 normal humans. Two tasks were used: (1) button pressing at imperative signal S1 and release at signal S2; (2) button pressing at imperative signal S2, preceded by warning signal S1. Together with a complex correlate of the CNV and EPs, the components of power decrease related to initiation of movement were not clearly identifiable in the central areas. They were sharply isolated in the occipital areas, using tone as the imperative signal. During initiation of movement a significant short-lasting decrease in power of the occipital alpha activities was observed in all 9 subjects. However, 'mu activity', tested in the classical manner and with help of power spectra, was not present in some of these subjects.