9i8 



HANDBOOK OF PHYSIOLOGY 



NEUROPHYSIOLOGY II 



Mc 

 Sc 

 Pc 

 Si 



tff 



iHiiiiiimii III 



Touch M II II II [ I 



Pul 



FIG. 21. Neuronal activity in the putamen followinc; various 

 afferent stimuli. Effects of single shock stimuli (7 v.; o. i msec.) 

 at arrow to contralateral median (A/e), contralateral sciatic (Sc), 

 contralateral peroneal iPc) and ipsilateral sciatic (Si) nerves. 

 Below: Responses elicited by lightly touching fur at base of tail 

 (touch) or by stretching the contralateral gastrocnemius muscle 

 {pull); application of such stimuli occurred approximately at 

 arrow. Downu'ard deflection represents a positive signal and 

 time calibration indicates 500 msec. [From Segundo & Machne 

 (231).] 



or the specific relay nuclei. In man intralaminar 

 thalamic stimulations induced recruitment waves 

 in the pallidum. 



Conversely pallidal stimulation may induce recruit- 

 ment waves in the human cerebral cortex mainly in 

 the homolateral hemisphere [Hassler (85, 86), Um- 

 bach (261)] (fig. 18). Spiegel & Wycis (243) and Um- 

 bach (261), however, found recruiting phenomena 

 and waxing and waning of cortical responses following 

 pallidal stimulation less constantly than after thalamic 

 stimulation. A clear di.stinction between recruiting 

 and augmenting potentials as described by Morison 

 in cats is not always possible in man. 



Ajmone-Marsan & Dilworth (2) and Shimamoto 

 & Verzeano (233) described recruiting waves in cats 

 after caudate stimulation at a rate of 8 per sec. similar 

 to those appearing after stimulation of nonspecific 

 thalamic nuclei. The experiments of Umbach (262) in 

 cats {encephale isole) showed that caudate stimuli of 

 low frequency cause constant spindle bursts in both 

 caudate nuclei, the motor cortex (mainly homo- 

 lateral), hippocampus and intralaminar thalamus. 

 During the slow wave in the caudatum wiiicii pre- 



cedes a spindle burst a silent period occurs in the 

 same structures which show spindles after caudate 

 stimulation. The effects of caudate stimulation can 

 be conditioned by stimulation of the reticular forma- 

 tion. The electrical activity of the caudate prefers 

 slow frequencies of 5 to 7 per sec. and even in con- 

 \ ulsions does not show higher frequencies than 15 to 

 25 per sec. During clonic convulsions the caudate 

 shows early rhythmic slow waves and silent periods 

 preceding other brain regions. This may indicate a 

 special role of the caudate in clonic convulsions. 

 Whether the caudate can induce the rhythm of 

 clonic discharges by intermittent inhibition as sug- 

 gested by Jung (131 ) is not yet clear. Electrical stimu- 

 lation of the caudatum sometimes but not regularly 

 can suppress convulsive activity in the rhinencephalon 

 and isocortex. Umbach's experiments give some addi- 

 tional evidence for an inhibitory function of the 

 caudate which tends to restrain excitation processes 

 in the brain. 



Microelectrode recording within the lenticular 

 nucleus and the claustrum of the cat was carried out 

 by Segundo & Machne (231). Their results are of 

 special importance for the afferent projection of 

 different modalities to the higher extrapyramidal 

 centers. They found that approximately two thirds of 

 the neurons of the putamen responded to various 

 somatic sensory stimuli mainly from skin and muscles, 

 as shown in figure 21. Activation as well as inhibition 

 of neurons was encountered. Inhibition (cessation of 

 unit firing) was apparent only in neurons of the 

 putamen, while activation with different latencies 

 was found in both pallidum and putamen. The tem- 

 poral pattern of response was distinctive for each type 

 or location of afferent stimuli. Association of somato- 

 sensory and vestibular effect was described as the most 

 common type of convergence on single neurons of 

 pallidum and putamen. One third of these neurons 

 reacted to vestibular stimuli by increase or decrease 

 of discharge. Effects from vagus nerve stimulation 

 were also found in the putamen. Olfactory, acoustic 

 or optic effects were exceptional but occasionally also 

 resulted in con\ergence with somatosensory affer- 

 ents. 



Segundo & Macime on the basis of their findings 

 have suggested that the motor functions of the striatum 

 and pallidum include a participation in the sensory- 

 motor regulation of complex behavior. These investi- 

 gations are a promising starting point for further 

 researches on single neurons of the extrapyramidal 

 system that will give us a more detailed insight into 

 the functions of the iiasal ganglia. 



