HANDBOOK OF PHYSIOLOGY 



NEUROPH^■SIOLOGY II 



a. Thalamic stimulation (centre median right 



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FIG. 7. Effects of stimulation of the thalamus during stereotaxic operations a, b: 62-year-old man 

 with trigeminal neuralgia. Stimulation of the right centrum medianum 2 to 5 mm above a sub- 

 sequent thalamotomy in the right nucleus arcuatus. Patient given chlorpromazine. a: EEG effects 

 of stimulating with a frequency of 8 per sec. From top downward.- Right and left precentral region, 

 right and left parietal region, and right and left occipital region. Recruiting waves appear in the 

 right precentral region, slow waves coming on after cessation of stimulation. Patient shuts eyes but 

 remains conscious, b: Stimulation at a higher frequency (50 per sec.) induces arousal with opening 

 of the eyes, although EEG waves are not blocked during stimulation. Upper right: Control before 

 stimulation of the thalamus. Middle right: Behavioral arousal produced by 8 per sec. g-v. thvratron 

 stimulation of the left anterior lamella medialis thalami in deep chlorpromazine-barbiturate anes- 

 thesia. Lower right: After thalamic stimulation in a 17-year-old imbecile. [From motion pictures 

 made by Hassler in collaboration with Riechert, Umbach and others; from Jung (135).] 



end in the thalamus. These thalamic nuclei recei\ing 

 afferent inflow from the pallidum may be considered 

 as a part of the extrapyramidal system. The most im- 

 portant are the nucleus ventro-oralis anterior (V.o.a., 

 the \-entroanterior part of nucleus ventralis lateralis 

 of Walker, \"L) and the nucleus lateropolaris (L.po or 

 VA). The medial nucleus (or nucleus dorsalis medialis 

 thalami) also receives numerous afferents from the 

 pallidum. Nuclei where fiber tracts coming from the 

 nucleus interstitialis, the vestibuloreticulothalamic 

 tract and the brachium conjuncti\um terminate are 

 also considered as belongino; to the extrapyramidal 

 system, although the brachium conjimctivum should 



rather be considered as an afferent part of the pyrami- 

 dal system. As the thalamic nuclei receiving afferents 

 from the pallidum are much smaller in carnivores 

 and rodeitts than in primates and man, little is known 

 yet about their responses to electrical stimulation 

 in cats. 



a) Nucleus ventromterinedius (I'.im). The nucleus 

 ventrointermedius projects to the cortex. In cats its 

 low-frequency stimulation produces a continuous 

 turning mo\ement of the head or the whole body 

 to the side of stimulation. The same effect is obtained 

 by stimulating its afferent pathway, the vestibulcj- 

 reticulothalamic tract. Destruction is followed by a 



