NEURAL SUBSTRATES OF DISCRIMINATIVE AVOIDANCE-LEARNING AND CLASSICAL EYEBLINK CONDITIONING IN RABBITS - A DOUBLE DISSOCIATION

In a previous study, lesions of the deep cerebellar nuclei blocked cla ssical eyeblink conditioning, but did not impair discriminative avoida nce learning in rabbits. Here, as also found previously, lesions of th e anterior and medial dorsal thalamic nuclei severely impaired discrim inative avoidance learning. However, these lesions had no impact on di scriminative eyeblink conditioning or reversal learning. These results complete the demonstration of a double dissociation, indicating disti nct neural substrates for the acquisition of these learned behaviors. It is proposed that the two learning circuits identified by these stud ies mediate, respectively, acquisition of specific adaptive reflexes a nd whole-body, voluntary goal-directed movements.