Passive avoidance conditioning and unitary activity in the basolateral amygdaloid nucleus of the rat.

Single unit activity was recorded in the basolateral nucleus of amygdala in rats in a passive avoidance test. Simultaneously, visual control of exploratory behaviour was carried out. Prior to establishing the conditioning, the mean frequency of the unit discharge was 14 Hz (SD = 9) and 1 minute after conditioning this unit activity decreased to values close to zero; later on (24 and 48 hours), a progressive recovery of the discharge was observed. Behavioural changes were also detected. The long term recovery of unit activity follows the time course of the extinction process. The possible significance of these findings is discussed in relation to some of the functional roles of this nucleus.