Aphasia and Associated Speech Problems (Paperback)

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1920. Excerpt: ... CHAPTER XII NEW CEREBELLAR FUNCTIONS In abstracting what we already know of the functions of the cerebellum, and in recounting some of the anatomical points involved, reference is had to the chapter on the physiology of the cerebellum in Starling'sil book, and to the fine little work by C. J. Herrick," 1916. With that function of the cerebellum which has to do with the maintenance of equilibrium and other changes in the posture of the body not especially connected with visual and auditory stimuli, namely, the vestibulocerebellar mechanism, we are not at all concerned, at least not primarily. With the matter of coordination, however, we are entirely concerned. The coordinating mechanism of the cerebellum depends on the reception of afferent stimuli from the muscles, joints and ligaments of the body; but as we are only discussing speech, only the muscles of speech need be mentioned. This system of afferent nerves has been called (by Sherrington8) the proprioceptive system, because it is not excited by changes in the environment, but only by changes within the body itself. Excitation o this system results in a regulation of the extent of motor discharge in the muscles and prevents over-action even though it may be evoked. It is a "compensatory reflex in an opposite direction to the reflex immediately excited from the skin." In this way, according to Sherrington, tone is maintained in muscles. Most of the speech defects, therefore, seen in tabes and Friedreich's ataxia are due to changes in tone and to disturbances of the regulative coordinative mechanism, resulting in ataxia and various types of dysphonia and dysarthria of ataxic character. The other proprioceptive part of the cerebellar mechanism, which really does not concern us in the discussion of speech...