[Analysis of the spike activity of the neuronal population of the motor cortex in the cat during a postural change conditioned reflex].

In experiments on untrained and trained cats the impulse activity of cortical neurons (area 4) was studied in response to long (1s) acoustic stimulus (conditioned stimulus for trained animals) and to a fall of the platform under the studied limb (unconditioned stimulus). Only those neurons were studied which responded to the appearance of passive movement after the fall of the platform. In trained animals the number of neurons responding to conditioned stimuli in case of realization of the reflex was 100% and in the absence of conditioned movements--70%. This largely exceeded the number of neurons responding to the same sound in untrained animals (45%). In peristimulus histograms of neuronal reactions of the studied population in untrained and trained animals (in the absence of conditioned movements) only the initial impulse response was clearly seen with the latency less than 50 ms and duration up to 100 ms. In the presence of conditioned movements the impulse response consisted of many components: initial response, early and late after-responses. The early after-responses with latency of 100-150 ms and duration of 100-200 ms were associated with the start of the conditioned stimulus, and the pattern and duration of the late after-responses was determined by the appearance of the conditioned movements. It is established that the value of neuronal response to reinforcement in trained animals does not depend on the appearance of the conditioned movement.