CEREBRAL REGULATION OF MOTOR COORDINATION IN MONKEYS FOLLOWING MULTIPLE TRANSECTION OF SENSORIMOTOR CORTEX

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Abstract
Multiple intersecting knife cuts were placed about 2.4 mm. apart in the cortical arm fields of 11 monkeys (9 Macaca mulatta, 2 Ateles geoffroyi). The incisions extended roughly through the gray mantle in a plane normal to the surface so as to interrupt and distort all patterns of horizontal intracortical transmission either of discrete excitations over neuronal pathways or of mass intercellular electrical currents. The cuts left intact the interconnections between separated cortical points by fibers through the medulla. When the incisions did not invade the subjacent white matter, the effect on motor coordination was extremely slight and transient. Deeper cuts extending through the transition zone of overlap between cortex and medulla produced a temporary depression of function from which recovery was rapid and complete. The symptoms, while they lasted, were entirely those of partial afunction, not dysfunction or disorganization, and they appeared to be correlated mainly with invasion of the medulla. When these deeper cuts were placed throughout the sensorimotor arm area including the depths of the fissures and with extensive overlap into neighboring cortical fields, first in one hemisphere and two weeks later in the other, the animals recovered thoroughly on each side in about three weeks. With the electrostimulable points for movement of shoulder, elbow, wrist, and digits, as well as the corresponding sensory foci permanently separated from each other as described, no functional disorganization could be detected. Electrical stimulation of the partitioned area after recovery evoked typical motor reactions and mass removal of the area produced a typical profound paralysis. The results fail to support those theories of brain function which ascribe an important role in cerebral organization to transcortical intragriseal irradiation either of discrete excitations over the fiber-work of the cortex or of patterns of intercellular electrical fields.
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