HUMAN EVOKED-POTENTIALS TO LONG-DURATION VIBRATORY STIMULI - ROLE OF MUSCLE AFFERENTS

Tonic vibratory stimuli of 1000 ms duration and different frequencies were delivered to muscles of the forearms of young human subjects. Evo ked potentials (EPs) were recorded from 29 scalp channels and revealed phasic highly lateralised and focally distributed EPs during the firs t 100 ms of the recording epoch that could be adequately modelled with a single point dipole source located in the vicinity of the central s ulcus contralateral to the stimulated arm. A later negativity with an onset of about 400 ms and a duration of about 800 ms was found to be s ymmetrically distributed over fronto-central regions. This negativity is interpreted in terms of cortical activation beyond the primary sens ory fields and could be related to the kinaesthetic phenomena experien ced during muscle vibration.