[Responses of neurons in the secondary somatosensory zone of the cat cortex during elaboration of a defensive conditioned reflex].

The neuronal responses of the somatosensory secondary cortex during the process of formation and extinction of a conditioned defence reflex to sound stimulus were studied in chronic experimentss on cats. In 21 out of 28 examined neurons a change in activity took place during the formation of a conditioned reflex as a response to the conditional signal. Two types of conditioned reflex responses were observed: excitatory and inhibitory ones. Most of the neurons excited by the conditioned stimulus responded during the first 50 ms, preceding the conditioned movement by 80-100 ms. Significant variability of neuronal responses was observed during formation of the conditioned reflex. After stabilization the neuronal responses to the conditioned stimulus acquired a stable from. During extinction of the neuronal conditioned activity a decrease of the discharge frequency in the excitatory neuronal response and disinhibition of the activity in the inhibitory responses were found.