SUBTHALAMIC HYPERKINESIA IN RHESUS MONKEY: EFFECTS OF SECONDARY LESIONS IN RED NUCLEUS AND BRACHIUM CONJUNCTIVUM

Abstract

Attempts were made to produce localized lesions of the subthalamic nuclei in 37 monkeys; such lesions produced choreoid dyskinesia in 19 monkeys. In 7 animals with unequivocal and appropriate dyskinesia, attempts were made to produce secondary lesions in the red nucleus or brachium conjunctivum. Secondary lesions of either the rostral or caudal halves of the red nucleus reduce the force, violence and amplitude of subthalamic dyskinesia, but do not abolish it. Secondary lesions of the brachium conjunctivum reduce choreoid activity, but produce homolateral ataxia and asynergia. It was concluded that release phenomena resulting from localized lesions of the subthalamic nucleus in the rhesus monkey and evidenced by choreoid dyskinesia, is not transmitted to segmental levels via the rubrospinal tract. The hypothesis was advanced that although neither the red nucleus nor the cerebellum can be considered primary sources of impulses released by removal of the inhibitory influences of the subthalamic nucleus, these structures contribute to the forceful-ness and violence of the dyskinesia.