Extrapyramidial mechanisms in handedness in the rat.

Abstract

Cerebellar destruction was produced in some rats with both pyramidal systems intact and in others with these systems destroyed. Assorted cortical and subcortical destructions were produced after the pyramidal systems were destroyed. With intact pyramidal systems unilateral cerebellar lesions did not influence handedness. Bilateral destruction of the pyramidal system abolished food-reaching habit, but relearning was possible. After such relearning, homolateral cerebellar destruction resulted in greater or less transfer of handedness and contralateral lesions to subcortical mechanisms (especially caudate nucleus) produced transfer. After bilateral pyramidal destruction, further cortical lesions did not affect transfer of handedness. No evidence was found that the effects of secondary destructions after bilateral pyramidal destruction were dependent on either the locus or mass of tissue destroyed by the secondary operations in the cerebellum or corpus striatum. It is concluded that the pyramidal systems of the cerebral cortex are the prepotent mechanisms in the control of handedness in the rat.