Effect of response inhibition in cat motor cortex neurons during the expectation of conditioning stimulus

The spike responses of the motor cortex neurons (area 4) associated with forelimb movement were studied in awake cats earlier trained to perform placing motor reactions. Responses produced by the same neurons were compared in two situations: 1) when a sound-click conditioning stimulus (CS) was applied in isolation; 2) when a CS followed a preliminary warning stimulus (WS), a light flash, with a 100–1000 msec delay. During the reflex initiation by combined action of the WS and CS, response components that occurred prior to the placing movement (PM) performance under isolated CS action weakened and arrived 50–150 msec later; yet, response components that appeared in the same situation simultaneously with PM onset or later remained unchanged. PM latent periods were not changed when WS was applied. The temporal interval between WS and CS was characterized by depression of neuronal activity; depression duration was determined by the interstimulus delay. It is conceivable that the described transformations in spike responses of cortical neurons occurred due to changes in the sensory direction of the animal's attention; this direction, in all cases, is a crucial factor in the formation of neuronal activity in the cortex.Translated from Neirofiziologiya, Vol. 25, No. 1, pp. 21–27, January–February, 1993.t