SUPPRESSION OF MAGNETIC MU-RHYTHM DURING PARKINSONIAN TREMOR

We recorded spontaneous magnetoencephalographic (MEG) activity and som atosensory-evoked fields (SEFs) with a 24-channel planar SQUIDgradiome ter in five patients with hemiparkinsonism. The SEFs of the patients w ere within normal limits. During tremorless periods, the spontaneous a ctivity over the somatomotor cortex had a frequency peak at approximat ely 10 Hz in all five patients and another at approximately 20 Hz in t hree. Tremor dampened the 10-Hz activity in all patients; in three the effect was bilateral. Tremor did not increase MEG activity at the tre mor frequency. The suppression of the mu rhythm by the parkinsonian tr emor resembled that occurring during voluntary movements in healthy su bjects.