Effects of Modulation of GABA- and Noradrenergic Transmission on Impulse Activity of Neurons of the Cat Motor Cortex Related to Realization of an Operant Reflex to the Action of Two Signals

On unanesthetized cats trained to perform placing movements to the action of two subsequent signals (warning and imperative stimuli), we examined reflex-related impulse activity (IA) of neurons of the motor cortex (field 4) and simultaneous changes in the "slow" cortical potentials (SCP) in the vertex zone. In almost all cases under study, the shift in the SCP toward negativity was associated with a decrease in the frequency of IA within interstimulus intervals; this corresponded to a period of focusing of the animal's attention on the expected imperative stimulus. Using a microiontophoretic technique, we tried to elucidate the role of GABA- and adrenergic cerebral systems in the genesis of such inhibitory periods. We conclude that, independently of each other but synchronously, both these systems can be involved in the maintenance of processes of active inhibition in the cerebral cortex under conditions of realization of an operant reflex.