Corticospinal responses to electrical stimulation of motor cortex in the rat.
Direct and indirect corticospinal responses to electrical stimulation of motor cortex were identified in urethane-anesthetized rats. 'Killed-end' recordings were taken from the corticospinal tract at the level of the cervical cord (C1-C2) and from the medullary pyramid. The identities of direct (D) and indirect (I) corticospinal responses were confirmed by: (1) removing motor cortex to eliminate I activity, and (2) pharmacologically increasing neocortical excitability, prior to any lesions, to increase I activity. Our data indicate that the conduction velocity of the fastest corticospinal fibers is approximately 18 m/s. Our identification of the components of the corticospinal response will permit the interpretation of the more complicated surface or 'non-killed-end' depth recordings which have shown particular utility in evaluating spinal cord damage.
Stewart
M
M
Department of Physiology, State University of New York, Health Science Center, Brooklyn 11203.
Quirk
G J
GJ
Amassian
V E
VE
D000200:Action Potentials; D000818:Animals; D004525:Efferent Pathways / Q000502:physiology; D004558:Electric Stimulation; D005071:Evoked Potentials; D008297:Male; D009044:Motor Cortex / Q000502:physiology*; D009431:Neural Conduction; D051381:Rats; D011919:Rats, Inbred Strains; D011930:Reaction Time; D013116:Spinal Cord / Q000502:physiology*