THE EXTRAPYRAMIDAL MOTOR SYSTEM 



917 



subcortical structures but did not pay special atten- 

 tion to extrapyramidal centers. Spiegel (238) re- 

 corded potentials from the thalamus. Jung & Korn- 

 mijller (136, 137) made a systematic study of the brain 

 potentials of the caudatum, putamen and thalamus 

 of rabbits, cats and monkeys, using a modified Hess' 

 technic of implanted electrodes. In unanesthetized 

 rabbits and cats they found periodic spindle-like 

 brain vvas'es appearing in the striatum nearly syn- 

 chronized with the contralateral striatum, the medial 

 thalamus and the motor cortex. After sensory stimuli, 

 flattening suggestive of desynchronization was re- 

 corded in the striatum, motor cortex and medial 

 thalamus simultaneously with evoked rhythmic waves 

 in the hippocampus. Accordingly a functional coor- 

 dination of the.se different brain structures was as- 

 sumed to exist although the anatomical connections 

 remained obscure, especially between the motor cor- 

 tex and the striatum. Jung & Kornmuller (137) sug- 

 gested in 1938 that bilateral connection of striatum 

 and motor cortex was induced by a 'third brain 

 structure.' In these early times the nonspecific 

 thalamoreticular system was unknown. One may now 

 assume that this coordination of periodic brain poten- 

 tials and desynchronization can be regarded as a 

 function of the nonspecific activation system. This 

 assumption is .supported by the findings of many 

 authors [Jung & Tonnies (138), Stoupel & Terzuolo 

 (248), Umbach (261, 262)] that stimulation of the 

 caudate elicits trains of cortical waves resembling the 

 recruiting potentials and that these waves show 

 highest amplitudes in the motor fields. The bilateral 

 synchronization of potentials found in the left and 

 right caudatum of cats and rabbits was explained by 

 Jung & Kornmiiller as the consequence of a common 

 pacemaker. Direct induction by the contralateral 

 caudate was rejected because convulsive potentials 

 did not spread from one caudate nucleus to the contra- 

 lateral one and because anatomical commissures 

 between the striata were lacking. 



When barbiturate anesthesia was given, Jung & 

 Kornmuller found the large slow potentials appearing 

 in the caudatum before they were seen in other brain 

 regions. This was confirmed later by Schneider and 

 co-workers (227) in a systematic study of narcosis. As 

 in animals, the spontaneous rhythms of the striatum 

 and pallidum in man do not differ essentially from 

 the cortical brain rhythms. Hayne et al. (93) described 

 somewhat faster alpha-waves from the human cau- 

 date than from the cortex. The putamen, pallidum 

 and surrounding structures had similar frequencies 



and amplitudes; the main source of the potentials 

 was found in the head of the caudatum and the 

 putamen. Knott and co-workers (151) found early 

 changes in caudate electrical activity at the onset of 

 sleep as did Hodes et al. (116) in the monkey. 



Our own experience during stereotaxic operations 

 in man failed to show regular or characteristic 

 changes of electrical activity of the basal ganglia in 

 extrapyramidal diseases. But Spiegel and co-workers 

 (244) observed a case of posthemiplegic athetosis 

 having brain waves of low amplitude in the contra- 

 lateral caudate. 



Alterations of sui:)cortical electrical activity under 

 the influence of drugs other than anesthetics were 

 described in cats with and without lesions of the basal 

 ganglia by Baker et al. (10), and Baird and his col- 

 leagues (g), and in a few cases of extrapyramidal dis- 

 eases by Spiegel et al. (239). Brain wave slowing after 

 chlorpromazine, meprobamate and bulbocapnine was 

 observed in the striatum and pallidum, chiefly in the 

 caudate nucleus. Increased sensitivity of the pallidum 

 to drug action was observed after homolateral cau- 

 date lesions by Baird and co-workers (9). 



Kennard & Nims (146) found that lesions of the 

 head of the caudate in monkeys were followed by 

 changes of cortical potentials showing more intense 

 'hypersynchrony' of the alpha waves. Combined 

 lesions of the motor cortex and the basal ganglia 

 caused the most marked changes. 



The effects of electrical stimulation of the basal 

 ganglia have been studied. Jung & Tonnies (138) 

 found incidentally that intralaminar thalamic stimu- 

 lation evoked potentials in the caudatum and hippo- 

 campus with lower threshold than in the isocortex 

 and that caudate stimulation es'oked recruiting-like 

 responses in the isocortex and allocortex. Ajmone- 

 Marsan & Dilworth (2) recorded recruiting responses 

 in cat caudate nucleus after stimulation of the non- 

 specific thalamic nuclei. Stimulation of the caudate 

 produced recruiting-like responses in the cortex of 

 shorter latency. Lesions of the caudatum affected 

 only slightly the cortical recruiting response but did 

 not abolish it. They concluded that the striate system 

 does not have an 'active' role in the production of the 

 recruiting response. 



In cats Spiegel et al. (239) found a close relationship 

 between the nonspecific thalamus, the caudate nu- 

 cleus and the pallidum after thalamic stimulation. 

 Recruiting potentials of the striopallidum were more 

 constantly (but not exclusively) obtained from the 

 nonspecific thalamic nuclei than from the association 



