The appearance of long-latency responses to a conditioned signal in the cortex is explained by strengthening of collateral connections between pyramidal neurons

Abstract

Experimental analysis and computer simulation of the neurophysiological processes underlying the "stable and local electrophysiological expression of conditioned reflexes" in the cerebral cortex, a phenomenon discovered in Asratyan's laboratory in the 1960s, showed that the long-latency components of cortical evoked potentials to a conditioned signal correspond to the late phases of the responses of motor cortex neurons, which are analogous to and probably generated by the same mechanism as long-latency epileptiform reactions of neurons in the epileptogenic cortex. Late long-latency components are generated via activation of NMDA receptors in the collateral connections between pyramidal neurons. The delay in the generation of responses depends on the initial activation of GABA(A) receptors and the slow kinetics of the current through NMDA channels. The appearance of late components as a result of training is explained by increases in the efficiency of collateral excitatory connections between pyramidal neurons.