Involvement of the amygdala in classical conditioning of eyeblink responsein the rat

The two-factor theory postulates that classical conditioning proceeds throu gh two stages, which support successive acquisition of emotional and motor responses. Emotional conditioning is thought to facilitate the subsequent a cquisition of the motor response. This form of interaction between the two stages of learning can be investigated while considering the central role o f the amygdala and the cerebellum in emotional and motor conditioning, resp ectively. Rats with bilateral lesions of the amygdala or the cerebellar int erpositus or intact rats were subjected to a fear conditioning session foll owed by four eyeblink conditioning sessions. Another group of intact rats w as subjected to eyeblink conditioning only. The CS in the fear conditioning session was a 73 dB tone, paired with a 100 dB noise-US. The same CS was p aired with a periorbital electroshock-US during eyeblink conditioning. Resu lts showed that fear preconditioning facilitated the subsequent eyeblink co nditioning among the intact groups. Amygdaloid lesions abolished this facil itatory effect of fear conditioning. These findings demonstrate that amygda la-mediated emotional conditioning facilitates the subsequent acquisition o f cerebellum-mediated motor responses. (C) 2001 Elsevier Science B.V. All r ights reserved.