THE EXTRAPYRAMIDAL MOTOR SYSTEM 



873 



FIG. 5. Contraversive turning and in- 

 activation produced by stimulation of 

 the caudate nucleus (intensity, i v. , rate, 

 8 per sec). Lrjt: Stimulation of the left 

 caudate nucleus near the internal cap- 

 sule causes ad\ersive movement of the 

 head and foretrunk to the right. Right: 

 Long-lasting (35 sec.) stimulation with 

 damped d.c. impulses elicits inaclivation 

 with incompletely closed eyes and pre- 

 served muscle tone in contrast to real 

 sleep. There is a slight contraversive 

 turning of the head. [From Hess (109) 

 and .\kert (3).] 



FIG. 6. Somatotopic representation of turning mosemcnts in 

 the caudate nucleus. Circles represent projections onto the 

 sagittal plane of the nucleus of points within the nucleus, stimu- 

 lation of which evoked these movements : solid circles, head 

 turning with or without body concavity to the opposite side, 

 concentric circles, neck and trunk movements plu.s contralateral 

 foreleg lifting; open circles, neck and trunk movements with fore- 

 leg Hexion plus contralateral lifting of the hind leg. The dis- 

 tribution of these movements in each third of the nucleus is 

 indicated by the numbers at the right. [From Forman & Ward 

 (61).] 



ful turning of the head and body to the contralateral 

 side [Hassler (8g)] which often becomes a circling 

 movement to the opposite side. These movements are 

 the result of well coordinated movements of the 

 extremities, the trunk and the neck (fig. 5, left). 

 Simultaneously, pupillary dilatation appears. In 

 similar studies, Forman & Ward (61) were able to 

 deinonstrate in the head of the caudate nucleus a 

 somatotopic localization (fig. 6). They showed that 

 ventral areas are responsible for contraversive head 

 turning combined with bending of the body, that 

 intermediate areas cause contraversive moxements of 

 the neck and trunk with lifting of the forelegs, and 

 that the dorsal areas cause the same effects with 



additional lifting of the contralateral hind leg. Ac- 

 cording to Hendley & Hodes (96) these contraversive 

 turnings depend upon an intact connection between 

 the caudate nucleus and medial parts of the nucleus 

 niger; according to our own anatomical studies, this 

 is also the area where direct caudonigral fibers termi- 

 nate. 



In further experiments Forman & Ward (61) 

 demonstrated the independance of these turning move- 

 ments of the corticospinal systems. When the motor 

 cortex and the caudate nucleus are stimulated simul- 

 taneously in unanesthetized cats, the effect of motor 

 cortical stimulation is not inhif)ited but a combination 

 occurs between contraversive turning and movements 

 of the extremities. Thus, it was not possible to confirm 

 the famous results of Met tier et at. (184) and of Hodes 

 et al. (116, 117) claiming a suppression of cortical 

 motor effects during simultaneous faradic stimulation 

 of the caudate nucleus. Howe\er, Forman & Ward 

 did observe suppression of running movements as a 

 result of stimulation of the putamen in one experi- 

 ment. 



A syndrome of striatal inactivation with poor 

 spontaneous activity and a deficient motor responsive- 

 ness to external stimulation occurs after longer 

 lasting, low frequency stimulation of the caudate 

 nucleus. Hess (105) described these effects as partial 

 (motor) sleep. Although the animals did not roll 

 themselves up before going to sleep, yawning some- 

 tiines resulted from caudate nucleus stimulation. 

 Sleep has also been found to follow caudate nucleus 

 stimulation in monkeys and man by Heath & Hodes 

 (94). Briefer and stronger stimulation of this structure 

 induces arrest of all spontaneous movements, the so- 

 called arrest reaction of Hunter & Jasper (123). 



Akert & Andersson (4) have also described an in- 

 activation syndrome evoked i)y caudate stiinulation, 

 as is shown in figure 5 (right), which merges into sleep. 



