Formation of a Conditioned Emotional Response (CER) Following Lesions of the Amygdaloid Complex in Rats

Abstract

Formation of a conditioned emotional response (CER), using suppression of food-reinforced bar-pressing as an index, was studied in a group of rats with amygdaloid lesions ( N = 5) and in a sham-operate control group ( N = 5). In contrast to control animals, which typically suppressed in two to three sessions, none of the amygdaloid operates met criterion within the set limit of 15 sessions or showed signs of suppression. Increasing the intensity and duration of shock also proved ineffective in these animals. Only by punishing each bar-press during the CS period could their responding be suppressed. Further tests on generalization of conditioned suppression, performed on two of the control animals, revealed relatively flat generalization gradients, consistent with other findings. Results were discussed in terms of amygdaloid effects on non-reinforced behavior in discrimination situations. “Inhibition” of responding associated with nonreinforcement appears to involve some of the same processes that operate in shock-motivated behavior.