HANDBOOK OF PHYSIOLOGY 



NEUROPHYSIOLOGY II 



creasing gravity and endurance of ataxia and hypo- 

 tonia as one moves up the primate scale toward man. 

 They also pointed out that more gross disturbances 

 follow bilateral lesions, and that tremor is not an ele- 

 ment of the syndrome unless the dentate nuclei are 

 involved. 



Partial lesions of posterior lohe. Experiments involv- 

 ing the isolated removal of lobules were clearly di- 

 rected toward the revelation of such topographical 

 organization as might exist in the posterior lobe. 



Several observers have reported cervical ataxia to 

 be the only sign following lesions of simplex (\'I, 

 H VI) in dogs (i86, 288, 344, 345). In a similar 

 fashion, dysmetria confined to the forelimb has been 

 reported to follow lesions of Crus I of the ansiform 

 lobule (H VII a) and of the hind limb after lesions 

 of Crus II (191, 288, 336, 344, 345) in both dogs and 

 monkeys. These observations have not been con- 

 firmed by more recent investigators (100, 121, 283, 

 284). Carrea & Mettler (62) in macaques and Cham- 

 bers & Sprague (67) in cats reported that lesions re- 

 stricted to the cortex of Crus I and Crus II were not 

 productive of symptoms. It was only when the under- 

 lying nuclei or the anterior lobe were involved that 

 cerebellar deficiencies were observed. 



In the cat (67, 121, 251, 252) and guinea pig (198) 

 ablation of the rostral lamellae of the paramedianus 

 (H VII b), related to the folium and tuber vermis, 

 resulted in ataxia confined to the foreleg. Ablation of 

 the caudal lamellae (H VIII a), related to the py- 

 ramis, resulted in ataxic signs confined to the iiind 

 leg. None of these observers noted any dynamic signs 

 or disorders of trunk or eye musculature. On the other 

 hand, when all of the paramedianus was removed 

 (67), signs resembling those following ablation of the 

 intermediate portion of the anterior lobe were ob- 

 served in mild and transient form. 



In the guinea pig (198) ablation of the folium and 

 tuber vermis (VII A, VII B) produced signs similar 

 to those seen following removal of the related lamellae 

 of the paramedianus. Chambers & Sprague (67) re- 

 ported that their cats exhibited increase of extensor 

 tonus, foreleg hypermetria, resting head tremor, and 

 a failure to react to light and sound which was inter- 

 preted as being due to inattention. 



Results of ablation of the paleocerebellar portion 

 of the posterior lobe have been inconstant. Guinea pigs 

 and macaques were free from deficiencies (62, 105, 

 198). The dog was reported to exhibit asthenia and 

 ataxia in the hind legs (288). The cat has been said 

 to dexelop weakness and atonia (322, 323) and to 



show signs resembling those following removal of the 

 anterior lobe (67). 



In an extended study, Di Giorgio and his colleagues 

 have demonstrated that the unilateral ablation of 

 large portions of the posterior lobe produces postural 

 asymmetries which are clearly defined by their tech- 

 niques of examination (98, 99, loi, 102). These asym- 

 metries disappear immediately following spinal cord 

 transection but reappear with the passing of spinal 

 shock to endure for hours. This residual effect on 

 spinal cord function develops within a few hours 

 following the cerebellar lesion and is not dependent 

 upon afferent supply or cerebrospinal supply to the 

 affected segments of the cord. The observations have 

 been confirmed in the pigeon (197). 



Efferent paths of posterior lobe. There are very few 

 studies of the effects of well-controlled lesions of the 

 intermediate and lateral nuclear groups made with 

 techniques whicli did not also damage large cortical 

 areas. 



Snider {302) has reported tremor, ataxia and slight 

 hypotonia ipsilaterally following unilateral destruc- 

 tion of the intermediate nucleus in the rabbit. Cham- 

 bers & Sprague (67, 68) also destroyed this nucleus in 

 the cat, producing a permanent lo.ss of ipsilateral 

 tactile placing. Their animals also exhibited a slug- 

 gishness of ipsilateral proprioceptive placing and of 

 hopping reactions for about one week. Accompanying 

 these signs were a mild increase in extensor tonus and 

 hypermetria in the ipsilateral foreleg. 



Lesions of the lateral nuclei in the cat (67) were not 

 productive of any alterations in tone or spinal re- 

 flexes, but placing and hopping reactions were de- 

 pressed and there was noted a poverty of limb move- 

 ment. Botterell & Fulton (31) reported that neo- 

 cerebellar decortication in the macaque produced 

 awkwardness, disturbances of gait and hypotonia 

 ipsilaterally. When such lesions were extended to in- 

 clude the lateral nucleus, the ataxia was more severe 

 and a transient tremor appeared. Carrea & Mettler 

 (62) reported intense ataxia and ataxic tremor to 

 follow dentate lesions in macaques. 



.■\ syndrome similar to that produced by large pos- 

 terior lobe lesions followed section of the superior 

 cerebellar peduncle in the macaque (259, 354). This 

 lesion failed to produce anv signs of release but pro- 

 duced atonia and ataxia ipsilaterally. The signs abated 

 in approximately 6 weeks but compensation was never 

 quite complete. Bilateral section increased the severity 

 of disturbance of voluntary mo\ement tremendously, 

 brought on kinetic tremor and delayed compensation. 

 Attempts to delineate the portions of tiie brachium 



