The effects of cerebellar lesions upon skilled movements and instrumental conditioned reflexes.

Eight cats were trained in reaching for food with their forelegs in cylinders 19-21.6 cm long of various diameters (3.9-10.1 cm). When the pre-operative training was completed, in six cats the interposite and dentate intracerebellar nuclei were destroyed, whereas in two cats the paravermal cortex was ablated. Interposite animals displayed big oscillatory movements around the entrance to the cylinder and overshooting in reaching for food with occasional forced grasping. Paravermal cats displayed overflexion leading to missing the entrance of the cylinder and wild batting movements observed in the large cylinder. The physiological mechanism of these disorders is discussed.