Observations on electrical stimulation of the cerebellar cortex

Abstract

In decere-brate cats with precollicular section the cortex of the anterior lobe of the vermis and the median part of the cortex of the lateral lobes of the cerebellum were stimulated with induced currents. When so stimulated the cerebellar cortex of these regions imposes a modification on pre-existing spinal reflex acts or states, but does not directly initiate them. Reflex inhibition and excitation of extensor muscles and reflex inhibition and excitation of flexor muscles have been found. It is probable that this result depends on the stimulation concurrently affecting intermingled nerve units of varying function in the cerebellar cortex. The predominant feature of a rapid stimulus series is inhibition of reflexes of the extensor group on the side stimulated. This is followed by a post-inhibitory rebound. The cerebellar cortex may exercise a pure excitatory effect of short latency on the reflexes of the extensor group. This occurs with weak series stimulation. In a slow series of break shocks, a single shock reveals both in extensor and flexor a biphasic response, i.e. inhibition followed by excitation or vice versa. When excitation precedes the inhibition, it can not be a rebound. All processes are of shorter latency in the flexor. Responses to a rapid repetitive series are the resultant of the relative values of these combined processes. The relationship of activity of extensor muscles to flexors of the same side is usually reciprocal, but it may be simultaneous. Flexor and extensor muscles of the contrary side are made active usually in the phase opposite to that of corresponding muscles of the stimulated side, but to a much less degree.