Myograms yielded by faradic stimulation of the cerebellar nuclei

The general characteristics of the muscular manifestations, which ensue on faradic stimulation of cerebellar nuclei, were described in a previous paper (28). In the present investigation an analysis of the nuclear responses was affected by recording the changes in tone in individual muscles of the foreand hindlimbs. Prior to our own work faradic stimulation had been applied to the cerebellar nuclei by Horsley and Clarke (17); they did not record the muscular changes graphically, but only observed the movements of the limb; these movements, to judge from their somewhat casual report, resembled those observed by ourselves. The belief that the responses observed by Horsley and Clarke were evoked by actual stimulation of the nuclei was clearly implied in their article; but in a paper by R. H. Clarke (6), published posthumously, the opinion is expressed that the reactions, supposedly of nuclear origin, were of a fallacious character, depending on current diffusion to Deiter's nucleus and various motor centres. Speaking more particulary for our own work we must state positively that our reactions were evoked by stimulation of the intracerebellar nuclei themselves, and were not due in any sense to spread of current beyond the cerebellum. Phenomena caused by spread of current are readily recognisable, and were avoided by using currents of threshold value for the nuclei, the excitability of which was carefully preserved. Our conclusions are thus more nearly in agreement with those of Horsley and Clarke than with those recorded in the posthumous paper of Clarke.