Basolateral amygdala lesions in the rat produce an abnormally persistent latent inhibition with weak preexposure but not with context shift

Abstract

Latent inhibition (LI) refers to retarded conditioning to a stimulus as a consequence of its nonreinforced preexposure. We have recently reported that basolateral amygdala (BLA) lesions lead to an abnormally persistent LI under conditions that normally disrupt LI, namely, extended conditioning. This study tested whether BLA lesions would induce abnormally persistent LI under two additional conditions disrupting LI in controls, namely, context shift and weak preexposure. LI was measured in an active avoidance procedure. In the first experiment, rats received 100 nonreinforced preexposures and were conditioned either in the same or in a different context from that of the preexposure stage. In the second experiment, rats received 50 nonreinforced preexposures and were conditioned in the same context as that of preexposure. Sham-operated rats showed LI in the same but not in the different context condition or with low number of preexposures. BLA lesions produced abnormally persistent LI with low number of preexposures but not with context shift. It is suggested that the BLA is involved in LI modulation based on the impact of preexposure and conditioning but not on contextual information.