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HANDBOOK OF PHYSIOLOGY 



NEURflPHYSIOLOGY II 



widespread bilateral responses (stronger contralat- 

 erally) from the cerebellar hemispheres and the more 

 posterior portions of the anterior lobes. In the mon- 

 key, Dow (io8) and Adrian (2) have reported some- 

 what finer degrees of localization. In this form, 

 stimulation of the sensory-motor areas of the cerebral 

 cortex is followed by responses which are most 

 prominent in the posterior portions of the vermian 

 and paravermian lobules and in the simplex — the 

 same areas which are activated by sensory impulses. 

 Indeed, Adrian emphasizes the convergence upon 

 similar cerebellar zones of impulses from the hind 

 liinb and hind-limb area of the sensorimotor cortex, 

 and from the forelimb and forelimb area of the 

 sensorimotor cortex, and froin the face and face 

 area of the sensorimotor cortex. The anatomical 

 description of these cerebral projections to the vermis 

 has been supplied JDy Nyby & Jansen (255). On the 

 other hand, other frontal areas of the cerebral cortex 

 (i, 124, 280, 360) project more strongly to the ansi- 

 form lobules over pathways which are independent of 

 and do not require the integritx' of the sensorimotor 

 cortex (108). 



Further associations between sensory projection 

 areas of the cerebral cortex and cerebellum have 

 been revealed by several studies directed to this 

 specific question (149, 152, 306, 307). In the anes- 

 thetized cat, Hampson (149) and Hampson et al. 

 (152) find that both auditory I and II project bi- 

 laterally to the folium and the tuber vermis only. 

 Stimulation of Soinatic I produced responses in the 

 contralateral anterior lobe and the simplex with 

 correspondence between hind limb, forelimb and face 

 areas. Somatic II was reported to be related to the 

 contralateral paramedian lobule, tuber vermis and 

 pyramis. An area of the medial surface of the hemi- 

 sphere, from which autonomic responses may be 

 evoked, projected to the ansiform lobule, lateral 

 anterior lobe and rostral portion of the paramedian 

 lobule. These results have been essentially confirmed 

 by Snider & Eldred (306) with the difference that 

 the latter investigators recorded evoked responses 

 from the paramedian upon stimulation of Somatic 

 I, found equivocal results from stimulation of Somatic 

 II and were able to detect activity only in the medial 

 folia of Crus I and II after stimulation of the auto- 

 nomic zone of the cerebral cortex. Similarly, in the 

 locally anesthetized monkey (307) convergence of 

 input from sensory and cerebral sources upon the 

 same cerebellar zone has been demonstrated by 

 stimulation of the primary sensory receiving areas of 

 the cerebrum. As might be expected from Combs' 



studies (75, 76), tlie localization of the cerebellar 

 response is evident only with threshold stimuli, and 

 the degree of overlap is considerable. 



Further evidence of cerebral influence on cere- 

 bellar function is furnished by the observation that 

 stimulation of the caudate nucleus is capable of pro- 

 ducing evoked responses in the ansiform lobule and 

 the tuber vermis (85). 



In a refreshingh different \ein, it has been reported 

 in preliminary form (166) that two different types 

 of e\'oked response may be recorded from the cere- 

 bellum following single shocks to the cerebral cortex 

 of the anesthetized cat. Short latency (2 to 5 msec.) 

 responses may be evoked by stimulation of Somatic 

 II while long latency (12 to 25 m.sec.) responses may 

 be evoked by stimulation of Somatic I. Both of these 

 responses are transmitted through the pontine nuclei. 

 The individuality of these responses is further at- 

 tested to by their different recovery cycles and by 

 differences in the conditioning effect of one upon the 

 other. 



IMPULSES FROM BR.MN-STEM SOURCES. Considering the 

 richness of cerebellar projections from various nu- 

 clear masses in the brain stem as deinonstrated ana- 

 tomically, there are relatively few reports of electro- 

 physiological studies of cerebellar activation from 

 these sources. Dow (107) has studied the cerebellar 

 responses to single stimuli delivered to the inferior 

 olive and to the lower bulbar reticular formation in 

 cats. Responses were recorded from the entire cere- 

 bellar cortex as a result of olivary stimulation. The 

 responses to reticular stimulation were different in 

 wave form from those evoked by olivary stimulation. 

 The latter were noteworthy for the prolonged de- 

 pression following a conditioning shock. Responses 

 evoked by stimulation of the pons were studied 

 (107). These were found to be distributed primarily 

 in the ansiform lobule (H V'll A), the paraflocculus 

 (H VIII B, H IX), the paramedian (H \ II B, 

 H \TII A) and the simplex and tuber vermis (V'll A, 

 \'II B). Smaller and inore irregular responses were 

 recorded from the spinocerebellar projection areas. 

 In a study of the responses to electrical stimulation 

 of the surface of the superior coUiculus, Snider (304) 

 recorded responses from the tuber vermis and the 

 simplex (\T, VII A, VII B). The author suggests 

 that cerebellar responses to visual stiinulation could 

 be mediated over tectocerebellar connections. 



iNTER.JiCTioNS OF SENSORY VOLLEYS. It has already 

 been indicated that convergence of impulses from 



