Fear-potentiated startle using an auditory conditioned stimulus: effect of lesions of the amygdala.

The effect of lesions of the amygdala on fear-potentiated startle using an auditory conditioned stimulus (CS) was evaluated, after replicating and extending previous findings that a tone is an effective CS for fear-potentiated startle. Rats received 10 tone-shock pairings on 2 successive days. At 24-48 hr following training, they received bilateral electrolytic lesions of the central nucleus of the amygdala or sham operations, and then were tested for fear-potentiated startle 4-5 days later. Lesions of the amygdala impaired fear-potentiated startle using an auditory CS, consistent with the previous findings using a visual CS. These data indicate that the effect of lesions of the amygdala on fear-potentiated startle is not specific to one sensory modality, consistent with the hypotheses that the amygdala is involved in processing multimodal information related to conditioned fear, or is part of an output pathway for motor and autonomic expressions of conditioned fear.