Specific functions of the motor cortex in reorganizing coordinations during motor training in animals and humans.

The involvement of the motor cortex in learning movements has recently attracted much attention. One aspect of motor learning is the inhibition of innate synergies which interfere with performance of the acquired movement. Various models of operant responses in dogs have demonstrated the critical role of the motor cortex in the reorganization and inhibition of interfering synergies during learning. The role of the motor cortex and corticospinal influences in the formation of new coordinations in humans was studied here in patients with organic lesions of the cerebral circulation involving the internal capsule, using postural coordination and movements in a bimanual unloading response as an example. Formation of the forearm stabilization response was deeply lesioned on the afflicted side. Some degree of impairment was also seen on the ipsilateral side, but it was no different from the level of learning impairment in patients with lesions not involving the internal capsule or in patients with parkinsonism. The existence of specific contralateral influences of the motor cortex and non-specific descending influences on the process of motor learning is proposed.