EFFECT OF SIDE AND RATE OF STIMULATION ON CEREBRAL BLOOD-FLOW CHANGESIN MOTOR AREAS DURING FINGER MOVEMENTS IN HUMANS

We measured, using single photon emission computed tomography, the reg ional CBF (rCBF) changes in the motor areas of 24 right-handed normal volunteers during the performance of a motor task consisting of sequen tial finger-to-thumb opposition. Twelve of them performed the task wit h their right and their left hands consecutively with a fast frequency and large amplitude. The other 12 subjects performed the task with th eir right hand only at a slow frequency and small amplitude. The contr alateral primary sensorimotor area (S1/M1), supplementary motor area ( SMA), and ipsilateral cerebellum were significantly activated during r ight and left finger movements performed at fast frequency and large a mplitude. No significant difference was found between the rCBF changes induced by the right dominant and left nondominant hands. When the ta sk was performed with a slow rate and small amplitude, the SMA was sig nificantly activated while no significant changes were observed in the contralateral S1/M1 or in the ipsilateral cerebellum. These results d emonstrate (a) that hand dominance evokes no differences in the activa tion of the main motor areas and (b) that the frequency and amplitude of the movement have a major effect on the quantitative and qualitativ e aspect of activation of motor areas in humans.