The effects of cortical epileptiform discharges on cuneate nucleus were investigated by studying cuneate field potentials evoked by corticofugal input. Cortical events triggered a negative-positive field potential sequence on the cuneate surface analogous to that evoked by forepaw nerve stimulation. Interaction of nerve-evoked potentials in the corticofugally induced positivity resulted in an amplitude decrease of the nerve potential, especially of its positive wave. Laminar analysis of the corticofugally evoked field potential suggested that its surface positive wave consisted of two components generated at different depths in cuneate; these two components were discussed as possible field potential signs of presynaptic and postsynaptic inhibition in cuneate. The influence of corticofugal discharges on transmission of sensory information through the cuneate nucleus was determined to be inhibitory, for nerve-evoked field potentials in the cuneate output pathway (medial lemniscus) were depressed during cortical epileptiform events.
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