Single unit reactions in the visual cortex of the unanesthetized rabbit to the light flashes of different intensities

Lateral inhibition as a possible mechanism for evaluating stimulus intensity

This article presents results obtained by simulation modeling of neural networks which show that lateral inhibitory connections between neurons can in principle, when the parameters of these connections are selected appropriately, support the existence in the CNS of detectors for the intensity of an acting signal. A condition for the operation of the proposed detection mechanism is the physiologically demonstrated fact of an inverse proportional relationship between the latency of neuron responses to a threshold stimulus and the intensity of this stimulus.

Increased regularity of activity of cortical neurons in learning due to disinhibitory effect of reinforcement

This paper reviews the author's studies on neurophysiologic mechanisms of conditioned reflex learning. Electroencephalograms, evoked potentials, activity of neocortical and hippocampal neurons and the rabbits' behavior in the course of elaboration of defensive and inhibitory conditioned reflexes to light flashes have been recorded. Electric shock (ECS) applied to the paw served as reinforcement. The study demonstrated three types of reinforcement effect on the activity of cortical neurons: activating, disinhibitory, and inhibitory. EEG activation due to reinforcement is accompanied by a change in phasic cortical neuronal activity from chaotic or irregular, typical of rest or inhibition, to regular tonic discharges (in neocortex and hippocampus) and group discharges in the stress rhythm, 5-7 Hz in the hippocampus. Following a number of conditioning trials, the effect of reinforcement is simulated by the effect of a conditioned stimulus. With EEG activation and increased regularity in impulses, facilitation of motor reactions is observed.