Cortical Representation and Functional Significance of the Corticomotoneuronal System

EXPERIMENTS by Adrian and Moruzzi1on the activity in the pyramidal tract of the cat indicated that in this animal the functional link between the pyramidal and the spinal motoneurones is not simple. In experiments on the same animal, Lloyd24showed that there is a complex relay system at the segmental level between the pyramidal fibers and the spinal motoneurones in the lumbar region. He found no evidence that the spinal motoneurones in the lumbar region of the cat are directly influenced by descending volleys in the pyramidal fibers, and this conclusion is in accordance with the histological findings of Szentágothai-Schimert.34In experiments on cats, we confirmed Lloyd's observation and found that pyramidal activation of the motoneurones in the cervical region of the same animal was also of internuncial order. On the basis of electromyographic studies in monkeys, Cooper and Denny-Brown * concluded that in this animal there