878 



HANDBOOK OF PHYSIOLOGY 



NEUROPHYSIOLOGY II 



euphoria may appear in the postoperative period, 

 as W'alker (286) also emphasized, but is also re- 

 versible. However, longer lasting changes, such as 

 decreased self-awareness, slightly decreased critical 

 capacity and decreased spontaneity or drive, com- 

 bined with a well preserved responsiveness to external 

 stimulation and an occasionally increased feeling of 

 well-being, were observed following pallidum lesions. 

 All these changes are much more pronounced after 

 bilateral almost complete coagulation of the pallidum. 

 Following this procedure performed in two stages, 

 some patients first go into a confusional state with 

 loss of orientation in time and space, with loss of 

 capacity to identify persons and the environment and 

 occasionally with .severe hallucinations. As long as 

 there is no complicating brain atherosclerosis and the 

 lesions are not too large, these syinptoms are also 

 reversible and nothing remains but a slight psycho- 

 organic syndrome. Here again, it is interesting to 

 note that bilateral destruction of the pallidum does 

 not produce any motor symptoms. In a few ca.ses a 

 slight akinesis relative to speech, respiration and 

 swallowing movements appears. However, this also 

 occurs in parkinsonian patients previous to the 

 operation. 



Experience with neurosurgical therapy of parkin- 

 sonism involving production of symmetrical almost 

 complete bilateral lesions in the pallidum indicates 

 that it may lead to such unfavorable psychological 

 changes that most neurosurgeons think it advisable to 

 avoid this type of operation. 



The pallidum is the site of pathological changes 

 in a number of disease entities, some of which may 

 be briefly noted. In icterus gravis of the newborn, 

 hypoxemic damage of the pallidum and nucleus sub- 

 thalamicus cau.ses demyelination and cell degenera- 

 tion, associated clinically with exaggerated mimetic 

 movements and motor reactions, athetotic hyper- 

 kinetic disorders of the muscles of the face, trunk and 

 limbs, and changing distribution of muscle tone. 

 Similar clinical manifestations appear in the Haller- 

 vorden-Spatz disease, where iron-free pigments 

 accumulate in the pallidum and nucleus niger, and 

 in the pure progressive pallidal atrophy of van 

 Bogaert. 



The status marmoratus [Anton (7), Vogt (266)] is 

 the result of vascular damage of the basal ganglia, 

 predominent in the putamen and caudate nucleus, 

 which occurs in early infancy. Cell atrophy is regu- 

 larly found in circumscribed areas in the external 

 pallidum. Athetotic motor disorders result from these 

 lesions. 



Carbon monoxide poisoning characteristically 

 causes symmetrical necrotic lesions of the dorsal 

 border of the internal and external pallidum, and in 

 the reticular zone of the substantia nigra. However, in 

 contrast to older views, it is unlikely that the.se lesions 

 result from hypoxemic injury since similarlv localized 

 damage of tlie pallidum can also be produced by 

 hydrocyanic acid, barbiturates, morphine, etc. 

 .Symmetrical necrosis of the pallidum does not always 

 lead to the parkinsonian syndrome if the patient 

 recovers; many patients show psychic changes only. 



As a result of damage to the external pallidum, the 

 neuronal systems of the internal pallidum, the nucleus 

 suiithalamicus, nucleus ruber and reticular formation 

 are disinhibitcd and out of control. Therefore the 

 neuronal pathways going from the nucleus ventro- 

 oralis anterior and nucleus lateropolaris of the thala- 

 mus to area 6aa and 6a/3 also convey excessive im- 

 pulse streams. Surgical interruption of this neuronal 

 chain and of the fibers feeding back from the extra- 

 pyramidal cortical fields decreases the numl:)er of 

 pathological impulses to the peripheral motor system 

 and thus leads to the clinically obser\ed decrease of 

 the athetotic hypcrkinesis. However, that there is 

 also a loss of control within the directly descending 

 pathways from the external pallidum to the reticular 

 formation and the subthalamic nucleus after surgical 

 interruption of the pallidothalamocortical systems 

 is shown b\' the fact that after weeks or months the 

 athetotic hyperkineses sometimes reappear. 



Diencephalic Structures 



NUCLEUS suBTHALAMicus : ANIMAL EXPERIMENTS. Stimu- 

 lation of this structure in animals, in the older ex- 

 periments of Karplus and Kreidl, Shinosaki, Ingram, 

 and Ranson and Hannett, produces mydriasis and 

 opening of the eyelids. Later Mella (180) and Waller 

 (288) produced rhythmic locomotor movements in 

 cats by stimulating in the vicinity of the subthalamic 

 nucleus. The best results were obtained in an area 

 lying medially to the nucleus subthalamicus in the 

 field H of Forel. Only by means of the Hess technique 

 of low frequency stimulation (8 per sec.) in unanes- 

 thetized freely moving cats was it possible to show that 

 these locomotor movements are actually turning or 

 circling movements toward the opposite side. These 

 contraversive movements appear at almost threshold 

 intensity. Mettler et al. (184) saw contractions of the 

 contralateral muscles of the back following stimulation 

 of the nucleus subthalamicus in monkeys and cats, 

 an obvious turning to tiie contralateral side appearing 



