The EEG analysis of the interrelationships of structures of the thalamofrontal system during the recovery of conditioned reflex behavior of amygdalectomized rats.

The influence of a unilateral lesion of the basolateral amygdala (BLA) on instrumental reflexes and the EEG activity of the orbitofrontal cortex (OFC) and the dorsomedial nucleus of the thalamus (DMN) was investigated in experiments on rats. A decrease in the number of correct reactions and an increase in their latency over the course of the first two postoperative weeks was accompanied by an increase in the amplitude of the delta and theta rhythms in the EEG of the OFC and DMN, whereas in the following two weeks this change appeared only in the EEG of the OFC. The changes in the EEG reflecting new functional relationships between the structures of the injured system were more prolonged (more than a month) than the period of the recovery of the parameters of the reflexes. It is hypothesized that an important role in the foundation of the disturbance and recovery of the instrumental reflex behavior following destruction of the BLA belongs to the functional reorganization of connections between the limbic and thalamocortical structures of the brain.