Abstract

This study was conducted to examine the effects of kainic acid lesion of the red nucleus (RN) on the learning-related neuronal activities of the cerebellar interpositus nucleus(INT) and the dorsal accessory inferior olive (DAO). Kainic acid(2mg/㎖, 0.4㎕) was injected to RN after the animals reached a criterion of acquisition in delay conditioning(300msec ISI). Behavioral CRs were severely impaired by the lesion with decreased amplitude and increased latency. The amplitude and the latency of UR were also affected by the lesion. However, the reflex facilitation of UR by CS-US pairing was maintained after RN lesion. The lesion of RN reduced the conditioning-related activities of INT throughout sessions. However, the patterns of the neuronal responses in CR/noCR trials, when analyzed separately, revealed that INT robustly showed the neuronal model of behavioral response in a few remaining CR trials with the RN lesion. DAO continued to show conditioning-related activities in both CR and noCR trials after the lesion. The results suggest that the lesion of RN does not simply block the performance of CRs, but results in a systematic alteration of the neural network including the cerebellum and the brain stem, which can establish the neuronal plasticity for the development and maintenance of CR.