Efferent fibers of the subthalamic nucleus in the monkey. A comparison of the efferent projections of the subthalamic nucleus, substantia nigra and globus pallidus

Abstract

A study was made to determine the efferent projections of the subthalamic nucleus in the monkey. Because of the impossibility of producing lesions in this nucleus, not involving adjacent structures, lesions were produced by different stereotaxic approaches. Comparisons were made with degeneration resulting from localized lesions in substantia nigra and globus pallidus. Degeneration resulting from these lesions was studied in transverse and sagittal sections stained by the NautaGygax method.Efferent fibers from the subthalamic nucleus pass through the internal capsule into the medial pallidal segment; a few fibers are distributed to the lateral pallidum. Some subthalamic efferent fibers pass to the contralateral globus pallidus via the dorsal supraoptic decussation, but none projection to the thalamus.Nigral efferent fibers project to parts of the ventral anterior (VAmc) and ventral lateral (VLm) thalamic nuclei. The medial pallidal segment gives fibers to: (1) ventral anterior (VA), ventral lateral (VLo) and centromedian (CM) thalamic nuclei, and (2) the pedunculopontine nucleus. The lateral pallidal segment projects exclusively to the subthalamic nucleus. Thalamic projections of the substania nigra and globus pallidus are distinctive. Subthalarnic projections to the globus pallidus are more profuse than those of the substantia nigra.Subthalamic dyskinesia, due to lesions in the subthalamic nucleus, is a consequence of removal of inhibitory influences acting upon the medial segment of the globus pallidus.The following hypothesis is presented:Clinicopathological reports (Martin, '27; Whittier, '47; Juba, '65) and experimental studies (Whittier and Mettler, '49b; Carpenter, Whittier and Mettler, '50; Carpenter, '61) indicate that discrete lesions in the subthalamic nucleus, which fulfill certain criteria, almost invariably results in severe dyskinesia in the contralateral extremities. This dyskinesia, the most forceful and violent variety known, has been referred to as hemiballism or hemichorea. Experimental studies in the monkey (Carpenter, Whittier and Mettler, '50; Carpenter, '61) suggest that this dyskinesia is the physiological expression of removal of inhibitory influences that normally act upon the neurons of the globus pallidus. This thesis is supported by the fact that lesions in the medial segment of the globus pallidus abolish or ameliorate the dyskinesia. Lesions in the ventral lateral nucleus of the thalamus also can reduce or abolish this form AM. J. ANAT., 121: 41-72.of dyskinesia (Martin and McCaul, '59; Andy and Brown, '60) presumably by interruption of pallidothalamic fiber systems and thalamocortical projections.Although a number of studies (Carpenter and Brittin, '58; Carpenter, Correll and Hinman, '60; Strominger and Carpenter, '65; Carpenter, Strominger and Weiss, '65; Stein and Carpenter, '65) have been done to establish structures involved in the neural mechanism of this dyskinesia in the monkey, many questions remain unanswered. A full understanding of the basic neural me...

Morphometric studies of the neuropathological changes in choreatic diseases

“…The pallidum gets its afferents from the striatum, the nucleus centromedialis thalami (Mettler 1945 ;Nauta and Whitlock 1954 ;Johnson 1961), the subthalamic nucleus (Whittier and Mettler 1949 ;Carpenter and Strominger 1967) (Johnson and Clemente 1959), the nucleus interstitialis (Hassler 1956), and the lem-niscus medialis (Mettler 1945), whereas afferents from the cerebellum are not unchallenged (Mettler 1968) and those from the cortex are questionable (Truex and Carpenter 1969) . Furthermore there are the afferents from the contralateral pallidum .…”

Connections of the Basal Ganglia and of the Cerebellum

“…IB). These GPl-subthalamic fibers, like the striato-nigral fibers, perforate the cere bral peduncle as components of the fasciculus lenticularis (FL) or 'comb' system [Nauta and Mehler, 1966;Carpenter and Strominger, 1967;Kuo and Carpenter, 1973].…”

“…The results of analysis of the efferent connections of the subthalamic nucleus by Carpenter and Strominger [1967] indicate that the nucleus projects mainly to the medial pallidus (GPm) ( fig. ID), a finding suggesting a relative short subcortical circuit: lateral GP->-subthalamic nucleus-vmedial GP.1 It should be noted that all three components of this circuit are selectively vulnerable to man ganese intoxication [Pentschew et al, 1963].…”

Changes in glutamate receptors in dyskinetic parkinsonian monkeys after unilateral subthalamotomy

“…The STN neurons in primates also project to the contralateral GP via the dorsal supraoptic decussation. 15 The strength of this efferent connection is currently unknown but may contribute to the results observed here. More studies are warranted to assess this observed discrepancy in outcomes between ipsi-and contralateral subthalamotomy.…”