[Responses of cat somatic cortex neurons during an instrumental placing reflex]

Neuronal activity from the areas 3 and 4 of the cortex was studied in cats during conditioned placing reaction. The neurons of the somatic cortex revealed comparatively late responses. The impulse reactions arose 80-100 ms after the conditioning signal but more frequently they were observed 200-450 ms later. In motor cortex the neuronal discharges preceded the movement by 50-550 ms, but in somatosensory cortex they occurred simultaneously or followed the initiation of the movement. Conditioned placing reaction and voluntary placing reaction were realized by the same neuronal mechanisms. The differential signal and the positive conditioning signal after extinction of the placing reaction evoked a short latent impulse reaction lasting 250-350 ms in the same neurons which participated in the placing reaction. Thus, neuronal reaction during the two types of the internal inhibition are excitatory at the beginning. The participation of neurons in the conditioned placing reaction, in its extinction, disinhibition and differentiation is determined by time reorganization of the excitation and is probably related to differentiated changes in the effectiveness of synaptic inputs of the neurons.