Abstract

Many researchers have distinguished two classes of conditioned responses: diffuse or nonspecific preparetory CRs and precise, specific, adaptive CRs. Specifically R.F. Thompson proposed that in aversive learning initial development of the nonspecific "conditioned fear" trace system may be essential for the subsequent development of the specific adaptive memory trace and that the neuronal substrates of the two trace systems differ at least in part. Considerable evidence indicates that amygdaloid central nucleus is involved in conditioned fear and cerebellum is involved in conditioned motor responding. This investigation was conducted to determine effects of amygdaloid central nuclus lesion on the course of the acqusition of rabbits nictitating membrane response(NMR) in classical conditioning. After lesion, acquision training of 4 days started, following one day of adaptation session. For each of the 4 days training, each subject received 60 trials of which 54 trials were reinforced and 6 trials nonreinforced. Only in nonreinforced trials were the heart rate changes measured and these changes were analyzed by comparing with the basal response rate. Conditioned NMR was analyzed by 9/10 criterion. There were significant differences between the sham-operated group and the amygdaloid central nucleus-lesioned group in heart rate changes and conditioned NMRs. The result suggests that amygdaloid central nucleus is involved in conditioned fear and the conditioned fear is essential for the specific adaptive response.