Bereitschaftspotential in patients with unilateral lesions of the supplementary motor area.

In the present study, an attempt was made to examine the sensitivity of the Bereitschaftspotential (BP) preceding simple finger movement in revealing pathophysiological patterns of premovement cortical activity in patients with chronic unilateral lesions of the supplementary motor area (SMA). Usually, in healthy subjects, BP has a clear maximum in Cz with larger amplitudes than in Ccon (located over the motor cortex, contralateral to the performing hand). In the patients, amplitudes did not differ between Cz and Ccon. This effect of the lesion on BP topography, was found in movements of either side. However, intraindividual comparisons revealed that the reduction of the BP in Cz (relative to Ccon) was larger for movements contralateral to the SMA lesion than for those ipsilateral of it.