[Changes in the spontaneous EEG-activity before and during voluntary self-paced movement. New ways of investigation of the central mu-activity (author's transl)].

Movement-related desynchronization was investigated in the EEG from central region in human subjects, during voluntary self-paced movement of the thumb. The average dynamic time-behaviour of the power in the alpha band was calculated from 4 sec before to 2 sec after voluntary movement. In all investigated subjects (9 students and 7 patients with several forms of hemiplegia) a significant power reduction before voluntary movement of the thumb was found. This power decrease can be interpreted as desynchronization of the central mu activity. Therefore, it appears that in all subjects a mu activity can be demonstrated. In most cases, a short-lasting desynchronization of central mu activity occurred about 2 sec before movement onset and was followed by a second one, about 1 sec before movement onset which reached a maximum during initiation of movement. Frequently the first desynchronization occurred in parallel but often also before the Bereitschaftspotential.