High resolution DC-EEG of the Bereitschaftspotential preceding anatomically congruent versus spatially congruent bimanual finger movements.

The purpose of the present study was to observe how the supplementary, cingulate and primary motor areas (SCMA, MI) participate in the spatiotemporal coordination of bimanual index finger movement and what role the SCMA plays. The Bereitschaftspotential (BP) was recorded using 64 channel direct current EEG (DC-EEG) to compare the anatomically congruent movements (abduction, adduction) with spatially congruent movements (both fingers to the right or left) in 16 normal volunteers. Subjects were required to move their two index fingers simultaneously in the horizontal plane (1) away from the midline (abduction), (2) toward the midline (adduction), (3) both index fingers to the right or (4) both fingers to the left. The results showed that there were significant differences (p<0.001) among the four tasks, across the 56 electrodes, and within the 20 different time points of the 3.5 s analysis epoch. BP amplitudes of the spatially congruent movements were significantly higher (p<0.05) than the ones of the anatomically congruent movements, and they were higher over the mesial wall motor areas SCMA than they were over the MIs. However, the significant differences differed between the left and right hemisphere in their amount and onset. The values of the difference ratio statistics between the SCMA and the MI indicated that the left hemisphere was more active than the right in our right-handed subjects for all tasks, particularly in the early (BP1) as compared to the late (BP2) component. Current source density mappings revealed that BP1 had its earliest onset in SCMA (6aalpha and 6abeta) for all four tasks. The onset times of BP2 were earlier and BP densities were higher in the spatially congruent tasks 3 and 4 as compared to the anatomically congruent tasks 1 and 2. Also, preparation (early component BP1) tended to start earlier and BP amplitudes tended to be higher for the spatially congruent tasks as compared to the anatomically congruent tasks.