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HANDBOOK OF PHYSIOLOGY 



NEUROPHYSIOLOGY II 



d) Nucleus ventro-arnlis atitnioi and nucleus laternpolaris. 

 The effects of stimulation or destruction of tliese 

 nuclei which recei\'e afferents from the pallidum are 

 not well known in cats because of their small size. 

 Both nuclei are much larger in man than the thalamic 

 terminal area of the brachium conjuncti\um. Stimu- 

 lation of these nuclei in Parkinson's disease, especially 

 of V.o.a., produces an acceleration and an increase 

 of the resting tremor or transitory block due to inter- 

 ference of the spontaneous rh\ thni with the stimulus 

 frequency. The effects of stimulation are less clear 

 than those following stimulation of the nucleus 

 ventro-oralis posterior. In athetosis, torsion dystonia, 

 ballism and chorea, it is possible to trigger the hyper- 

 kinetic phenomena during quiet intervals by stimu- 

 lating nucleus V.o.a. and L.po. The hyperkinesia 

 produced by electrical stimulation outlasts the end of 

 the stimulation. In some conscious patients with a 

 parkinsonian syndrome, stimulation of this nucleus 

 was followed by conjugate eye movements to the 

 contralateral side (the head being fixed), concomitant 

 violent lifting of the contralateral arm and excited 

 utterance of unintelligible sounds comparable to the 

 syndrome described as following stimulation of 

 Penfield's supplementary motor area. 



Destruction of both nuclei in patients with torsion 

 dystonia and athetosis improves and sometimes even 

 suppresses the hyperkinesia without causing any 

 paralysis. In athetosis, however, the symptoms usually 

 reappear. Simultaneous destruction in Parkinson's 

 disease of nucleus \'.o.a. and \'.o.p. decreases or even 

 completely abolishes the rigor. At first there is even 

 a hypotonia, although the paralysis is \ery slight 

 or even absent. Pre\iously missing associated move- 

 ments may reappear. The posture is so fundamentally 

 changed after such operations that it is almost im- 

 possible to recognize the previous parkinsonian disease 

 in these patients. Postoperative motor impairment 

 has not been observed. Some of the patients, how- 

 ever, have to be persuaded after the operation to 

 persev'ere in using the limb pre\iously immobilized 

 ijy rigidity. Learned movements are also unimpaired. 

 Bilateral symmetrical lesions are contraindicated 

 because of the consequent personality changes of the 

 frontal lobe type which result froin the interruption 

 of passage fibers of thalamofrontocortical pathways. 



e) .Xucleus ventro-oralis internus. .Stimulation of this 

 nucleus and of its afferent fiber tracts from the nucleus 

 interstitialis produces a rotary movement of the head 

 to the ipsilateral side. In cats the effect involves the 

 head and the anterior bod\-. Destruction produces 

 onlv verv transitorv effects such as a rotation of the 



head to the opposite side. The sites of stimulation for 

 the arrest reaction described by Hunter & Jasper 

 (122, 123) are located in the medial part of this 

 nucleus (close to the anterior intralaminary nuclei). 

 In man stimulation of this nucleus produces a con- 

 traction of the muscles of the contralateral neck and 

 shoulder, of the sternocleidomastoid and of the facial 

 muscles. Simultaneously, an arousal effect some- 

 times with smiling appears. In spasmodic torticollis, 

 destruction of this nucleus reduces the rotary move- 

 ments to the ipsilateral side but not to such an extent 

 that it would be sufficient by itself for a satisfactory 

 therapeutic effect. 



Mesencephalic Structures 



NUCLEUS NIGER. Early studies of the effects of stimu- 

 lation of the region of the nucleus niger in animals, 

 made by von Bechterew (273), Jurman (139) and 

 von Economo (274), showed bilateral rhythmical 

 chewing and swallowing movements to be the princi- 

 pal motor responses. However, later investigators 

 failed to find any definite motor effects. 



According to Mettler (181) stimulation of the 

 nucleus niger increases the extensor tonus of both 

 anterior limbs in cats, even after destruction of the 

 motor cortex. Mettler and co-workers (184) also 

 thought that stimulation of the nucleus niger reduces 

 the amplitude of the phasic mo\ements resulting 

 from simultaneous cortical stimulation and tends to 

 produce a tremor. As Folkerts & Spiegel (60) were 

 able to show, stimulation of the reticular formation 

 produces tremor only when the nucleus niger had 

 been previously destroyed. Wycis et al. (297) showed 

 that this tremor could be obtained also after degenera- 

 tion of the brachium conjuncti\um, thus demonstrat- 

 ing that it does not depend on participation of the 

 brachium conjunctivum. This is in contrast to the 

 view of Carrea & Mettler (35) who considered lesions 

 of the ventral part of the brachium conjunctivum 

 to i)e responsible for the tremor without stimulation. 



According to older observations destruction of the 

 nucleus niger in dogs and cats does not usually pro- 

 duce disorders of motor activity or muscle tone 

 [von Bechterew (273), von Economo & Karplus 

 (275)]. Only D'Abundo (37) observed choreoid 

 movements and later rigor in newborn cats following 

 lesions in the substantia nigra and in parts of the 

 mesencephalon. Bishop et al. (12) and also Peterson 

 et al. (210) were able to produce postural tremor by 

 means of small localized lesions in an area dorsal 

 and medial to the nucleus niger, intermediate between 



