| Abstract: | The distribution of focal potentials over the cross section of the 7th cervical segment of the spinal cord was studied during stimulation of the pyramids, the red nucleus, and a peripheral nerve (ulnar) in adult cats anesthetized with chloralose and Nembutal. The earliest focal potentials in the fasciculus dorsolateralis were recorded 1.4–1.5 msec after stimulation of the pyramids and 0.8–0.9 msec after stimulation of the red nucleus. These times correspond to maximal condution velocities of 56–68 and 105–124 m/sec respectively. The earliest post-synaptic activity in response to pyramidal stimulation was found in the lateral areas of laminae V and VI, and in response to stimulation of the red nucleus in laminae VI and VII in Rexed's classification. The pyramidal wave also evoked considerable postsynaptic activity in medial areas of the dorsal horn. In response to stimulation of peripheral afferents activity was evoked in neurons in the central and medial parts of laminae V and VI. It is postulated on the basis of these results that corticospinal and rubrospinal fibers may be connected monosynaptically with specialized interneurons, free from peripheral influences, in the lateral areas of laminae V and VII respectively; in the lateral part of lamina VI convergence of both types of influences on the same cells is possible. Interaction between descending and afferent influences possibly takes place on more medially located neurons.A.A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 4, No. 2, pp. 158–167, March–April, 1972. |
