Different lateral amygdala outputs mediate reactions and actions elicited by a fear-arousing stimulus

Fear-arousing stimuli elicit innate reactions and can reinforce acquisition of new responses. We tested whether mechanisms mediating these conditioned stimulus (CS) properties were isomorphic or dissociable within the amygdal a. Rats trained on a fear-conditioning task (CS paired with footshock) were then trained on an escape-from-fear task (EFF) in which the CS reinforced a locomotor response terminating the CS. Lateral nucleus (LA) lesions block ed acquisition of both conditioned freezing responses and the CS's reinforc ement of a new response in the EFF task. Central nucleus (CE) lesions block ed conditioned freezing but not the EFF, whereas basal nucleus (B) lesions blocked the EFF but not conditioned freezing. Thus, activation of the LA by a CS seems to trigger conditioned reactions via CE and conditioned aversio n via B activation, reduction of which reinforces new actions.