Lesions of substantia nigra retard pavlovian somatomotor learning but do not affect autonomic conditioning.

New Zealand albino rabbits with bilateral radio frequency lesions of the substantia nigra (SN) were compared with sham-operated animals on a pavlovian conditioning task in which eyeblink (EB) and heart rate (HR) responses were concomitantly assessed. Lesions of SN increased the number of trials required to reach an EB learning criterion but left the HR conditioned response intact. These results together with other reports in the literature suggest that extrapyramidal motor structures are involved in mediating somatomotor conditioning but are not involved in autonomic learning.