Cerebellar evoked potentials and motor evoked potentials in the spinal cord of rats.

In rats, the cerebellar evoked potentials (CEPs) were monitored along the spinal cord following the electrical stimulation of cerebellar cortex. The CEPs monitored at thoracic and lumbar cord consisted of from 1 to 3 waves with conduction velocities of 16-20.28 m/sec. The amplitudes of these waves declined dramatically as the frequency of the stimulation increased above 50 Hz, indicating that the CEPs were either evoked or conducted polysynaptically. The pathway conducting CEPs were studied using acute spinal cord lesioning and intracord recording methods. The pathways conducting CEP and MEP were also compared in the same preparation in controlled spinal-cord-lesioned animals. The CEPs were mainly conducted along the ventral and lateral funiculi where the reticulospinal tracts and the vestibulospinal tracts are located. Simultaneous disappearance of both MEP and CEP after controlled spinal cord section seems to suggest the 2 different evoked potentials are conducted along the same pathways in the spinal cord of rats. Species difference in conduction pathways of MEP and CEP were compared and discussed.