[Evoked potentials during elaboration of fine differentiations].

The paper deals with the character of changes in the EP form recorded from the visual cortex of a rat during elaboration of a system of positive and negative (with different degree of precision) conditioned defensive reflexes. It has been shown that in a state of a consolidated habit of pain stimulus avoidance in a shuttle box a negative component with peak latency up to 70 msec develops in EP to the differentiation stimulus of 0.5 c/s. This component is much less pronounced to the 2 c/s conditioned stimulus. When a more precise differentiation stimulus (1 c/s) was presented to the animal in this state the development of the studied component depended on the subsequent behavioural reaction: it developed if the animal reacted in the same way as to the differentiation stimulus. This fact suggests that the generation of this component is connected with the inhibitory processes developing at the time when the animal is choosing its behavioural reaction.