912 HANDBOOK OF PHYSIOLOGY ^ NEUROPHYSIOLOGY II 



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; 8/sGC I sec 



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5o/sec arousal opens eyes 



FIG. 1 8. Nonspecific effects of pallidum stimulation on the human EEC. Recruiting potentials 

 at 8 per sec. and desynchronization with arousal at 50 per sec. stimuli. During stereotaxic operation 

 on a parkinsonian patient the right internal posterior pallidum was stimulated by thyratron im- 

 pulses preceding coagulation. Upper record; 8 per sec. stimulation (12 v. peak strength) elicits re- 

 cruiting waves mainly in the homolateral right ire) frontoprecential region with increasing ampli- 

 tude and some waxing and waning, less effect in the contralateral (/;) region. Lower record; 50 per 

 sec. stimulation (4 v.) through the same leads causes acceleration of rhythms and some flattening 

 following the stimulus series. Some alpha waves continue in the first 300 msec, of stimulation. 

 Arousal with opening of the eyes appeared during stimulation. [From Umbach, unpublished obser- 

 vations.] 



arousal type of EEG and gamma activity causing 

 muscle spindle discharge found by von Euler & 

 Soderberg (276). 



At higher diencephalic levels of the thalamo- 

 reticular system coordination with extrapyramidal 

 structures becomes very close. Hess described as 

 Adynamic a syndrome showing loss of muscle tone and 

 spontaneous activity occurring after coagulation ot 

 the posterior hypothalamus (see fig. 17). He called 

 this region bordering the oral part of the mesence- 

 phalic reticular formation the 'dynamogenic' zone. 

 Adynamie seems to be a milder variant of the syndrome 

 that Magoun and his school found after coagulation 

 of the anterior mesencephalic mid-line region in cats 

 and monkeys which resulted in a coma simulating 

 sleep with marked slowing of EEG rhythms [Lindsley 

 & co-workers (163, 164)]. 



Among the direction-specific eflfects of mesodio- 

 encephalic stimulation described by Hess, the body 

 raising responses evoked from the lower mesodience- 

 phalic structures, the prestitial and red nuclei (figs. 

 8, I 7) have special importance for the waking attitude 

 and the posture of attention. 



The motor patterns of attention are regulated by 

 the extrapyramidal mechanisms in close association 

 with the tegmental motor system. This system, the 

 nucleus motorius tegmenti {motorischer Hanbenkern) of 

 Edinger (52), includes, besides the eflferent motor 

 nuclei of HI, IV, V, VI, VII, and IX to XII cranial 

 nerves, tiie red nucleus and the nucleus vestibularis 

 of Deiters, and also the reticular formation. A number 

 of rhythmic motor phenomena, such as nystagmus 

 and respiration, are regulated by this system. Among 

 these are the opening of the eyes or adversive move- 



