Cerebellar and Brainstem Circuits Involved in Classical Eyeblink Conditioning

Model systems are one useful strategy for the investigation of the mechanisms of learning. Whereas mammalian model systems generally do not offer the ease of identifying circuitry and exploring cellular mechanisms of learning that is realized with invertebrate preparations /37,97/, research involving the rabbit classical eyeblink conditioning paradigm has now reached the state at which much of the basic conditioning neural circuit appears to have been identified /9,65,66,85,89,91/. Despite a dispute as to precisely where in the circuitry convergence of the associated stimuli may occur, there is substantial evidence identifying the stimulus input pathways and motor output pathway. The present summary of this research details these paths. In addition, the proposed sites of convergence of the conditioning stimuli are discussed. Finally, a hypothesized neural circuit responsible for classical eyeblink conditioning is presented along with some suggestions for future research directions.