Role of the supplementary motor area and the right premotor cortex in the coordination of bimanual finger movements

Abstract

To obtain a better understanding of the cortical representation of bimanual coordination, we measured regional cerebral blood flow (rCBF) with 15O-labeled water and positron emission tomography (PET). To detect areas with changes of rCBF during bimanual finger movements of different characteristics, we studied 12 right-handed normal volunteers. A complete session consisted of three rest scans and six scans with acoustically paced (1 Hz) bimanual, mirror, or parallel sequential finger movements. Activation of the right dorsal premotor area (PMd) extending to the posterior supplementary motor area (SMA) was significantly stronger during the parallel movements than during the mirror sequential movements (p < 0.05, at cluster level with correction for multiple comparisons). To determine whether these cortical areas truly represented bimanual coordination, a different group of nine normal volunteers was studied with a different task. Subjects performed acoustically paced (2 Hz) abduction-adduction movements of the index finger, making right only, left only, and bimanual mirror and parallel movements. Activation of the posterior SMA and right PMd was significantly greater during the parallel movements than during the bimanual mirror movements or the unimanual movements of either hand (p < 0.01, with anatomical constraint). Thus, the posterior SMA and right PMd appear to be related to the bimanual coordination of finger movements.

Fig. 1.

Comparisons of adjusted mean rCBF between bimanual, sequential parallel movement and mirror finger movements, superimposed on typical magnetic resonance images unrelated to the study’s subjects. Six transaxial images of 40, 44, 48, 52, 56, and 60 mm above the anterior–posterior commissural line are shown. The pixels show levels of statistical significance above p < 0.05 for its spatial extension of activation after thresholding atZ > 2.3. Vertical red lineindicates midsagittal plane, crossing horizontal red line at the vertical anterior commissural line (VAC).

Fig. 2.

Comparisons of adjusted mean rCBF between bimanual, abduction–adduction, parallel, and mirror movements of the index fingers. Three transaxial images of 40, 44, and 48 mm above the anterior–posterior commissural line are shown. The pixels showZ > 2.3. The activated foci are corresponding to that of sequential finger movements, with lesser significance.