Effect of side and rate of stimulation on cerebral blood flow changes in motor areas during finger movements in humans.

We measured, using single photon emission computed tomography, the regional CBF (rCBF) changes in the motor areas of 24 right-handed normal volunteers during the performance of a motor task consisting of sequential finger-to-thumb opposition. Twelve of them performed the task with their right and their left hands consecutively with a fast frequency and large amplitude. The other 12 subjects performed the task with their right hand only at a slow frequency and small amplitude. The contralateral primary sensorimotor areas (S1/M1), supplementary motor area (SMA), and ipsilateral cerebellum were significantly activated during right and left finger movements performed at fast frequency and large amplitude. No significant difference was found between the rCBF changes induced by the right dominant and left nondominant hands. When the task was performed with a slow rate and small amplitude, the SMA was significantly activated while no significant changes were observed in the contralateral S1/M1 or in the ipsilateral cerebellum. These results demonstrate (a) that hand dominance evokes no differences in the activation of the main motor areas and (b) that the frequency and amplitude of the movement have a major effect on the quantitative and qualitative aspect of activation of motor areas in humans.