The effects of cooling supplementary motor area and midline cerebral cortex on neuronal responses in area 4 of monkeys.

It has been postulated that the supplementary motor area (SMA) is involved in the initiation of movement and in gating of afferent input to motor cortex (MI) from peripheral receptors. We studied the responses of 119 neurons in MI to imposed disturbances of wrist-movement performance generated by the introduction of torque pulses before, during and after localized cooling of the SMA in conscious monkeys. The cooling of SMA did not prevent monkeys from making these simple movements. Eighty-two neurons responded to the wrist perturbations. Only 7 of these neurons changed their responsiveness with unilateral or bilateral cooling of SMA. From the data we have obtained on MI neuronal firing patterns, the SMA does not appear to modulate the long-latency trans-cortical stretch reflex during the periods in a task that we have investigated. Nor does it prevent animals from performing these simple movements to a visual target.