[270 



HANDBOOK OF PHYSIOLOGY 



NEUROPHYSIOLOGY II 



ANTERIOR LOBE OF CORPUS CEREBELLi. Destruction of 

 Cortex. The results of destruction of the anterior lobe 

 and its efferent paths complemented the results of 

 stimulation of the same structures and revealed that 

 the dynamic signs of release from inhibition were due 

 to encroachment upon this portion of the cerebellum. 

 Rothmann (288) seems to have been the first to 

 make the association between the anterior lobe and 

 the opisthotonus and extensor rigidity which followed 

 its complete removal. Rothmann also demonstrated 

 that the more caudal portions of the vermis (\T-IX) 

 were responsible in part for the compensation which 

 occurred, for if they were later removed the signs of 

 inhibitory withdrawal were repeated in a more in- 

 tense and enduring fashion. It is noteworthy, however, 

 that the signs of spasticity were not the sole results of 

 Rothmann's ablations, for his animals demonstrated 

 ataxic gait and tremor in the iiead and trunk as well. 

 There is general agreement about the validity of 

 Rothmann's findings for the quadruped (24, 67, 185, 

 313, 339). Snider & Woolsey (313) observed addi- 

 tionally that the spastic manifestations are greatly 

 accentuated b\' removal of the pericruciate cortex as 

 well, an observation which has been fulK' confirmed 



(>85). 



The situation following anterior lobe (I-\') ablation 

 is not as clear for the primate. Fulton & Connor (125) 

 reported that exaggeration of postural tonus and re- 

 flexes and increased tendon refle.xes were produced 

 in the macaque (II-V) along with gross disturbances 

 of coordination of the limbs and head movements 

 and tremor. Connor & German (78) uniquely re- 

 ported opisthotonus in this form. On the other hand, 

 Carrea & Mettler (62) observed no release phe- 

 nomena in the macaque following incomplete lesions. 

 Soriano & Fulton (314) reported that whereas release 

 phenomena were not observed after anterior lobe 

 ablation in the macaque, this could be made evident 

 in exaggerated and enduring form by subsequent re- 

 moval of cerebral motor areas. Some of the above ob- 

 servations have been reported only in abstract form 

 without histological studies, but the general mildness 

 of the signs and their short duration recall the results 

 of complete ablation in the macaque (34, 69, 327) 

 and the paucity of inhibitory responses to stimulation 

 of the anterior lobe in the macaque (151, 310). 



Further evidence of the inhibitory action of the 

 anterior lobe was obtained from observations of the 

 increase in decerebrate rigidity which follows in- 

 activation of this portion of the cerebellum in the 

 quadruped (32, 45, 58, 59, 105, 196, 236, 262, 299). 

 This change was evident only on the ipsilateral side 



of the body if the inactivation was unilateral (32, 



45. 59)- 



Earlier attempts to assign somatotopic areas within 

 the anterior lobe were unsuccessful (288). However, 

 Chambers & Sprague (68) noted that lesions con- 

 fined to the medial portion of the anterior lobe pro- 

 duced the signs of spasticity with extensor rigidity, 

 whereas lesions confined to the intermediate portion 

 resulted in an increase in resting flexor tonus in the 

 forelimb and flexion hypermetria during walking. 

 In a more extended study of the results of discrete 

 cortical lesions in the vermis of the cat (67) these in- 

 vestigators came to the conclusion that each half of 

 the entire medial vermis was involved in the control 

 of postural tonus, locomotor activities and equilibrium 

 for the whole body. The more laterally placed inter- 

 mediate portions, on the other hand, were thought to 

 be related to ipsilateral postural reflexes and indi- 

 vidual movements. They reported somatotopic or- 

 ganization in both portions of the vermis, with more 

 overlap medially than in the intermediate portion. 

 They assigned the tail to the lingula; the hind legs 

 and pelvic girdle to the centralis and rostral culmen; 

 the forelegs, pectoral girdle, head and neck to the 

 caudal culmen; and the head, neck and eyes to the 

 folium and tuber vermis. 



Efferent paths. The results of studies of nuclear 

 lesions produced by techniques involving extensive 

 cortical damage were not easily interpretable and will 

 not be dealt with here. With the use of the stereotaxic 

 technique, the cerebellar nuclei may be destroyed 

 with insignificant damage to the cerebellar cortex 

 and are therefore susceptible of interpretation. How- 

 ever, it is important to remember that the crossing 

 fastigiobulbar fibers course through the nucleus of 

 the opposite side, so that it is impossible to produce 

 unilateral signs bv unilateral fastigial destruction 



(169). 



Complete destruction of the fastigial nuclei in the 

 intact cat (13, 14, 17, 185) produced signs of release 

 from inhibition without atonia. However, unilateral 

 destruction of the fastigial nucleus in the intact cat 

 (13, 14, 17, 316) produced signs of spasticity contra- 

 laterally only, whereas the ipsilateral posture was 

 flexor, and atonia was demonstrable ipsilaterally for 

 several weeks. If, following such lesions, the vermian 

 cortex was removed (316), the laterality of the signs 

 reversed. Batini & Pompeiano (13, 14, 17) report 

 that ipsilateral atonia and contralateral spasticity 

 were also produced if only the anterior half of the 

 nucleus was destroved. If onlv the caudal half was 



