The striatum and the globus pallidus : studies of internal and external organisation in the basal ganglia

• Main Author: Walker, Ruth Helen
• Published: University of Edinburgh 1992
• Subjects: 612.8
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.663382

The basal ganglia are crucial for the processing of motor commands received from the cerebral cortex, as is demonstrated by the disorders which following lesions of this area. For example in humans, Parkinson's disease and Huntingdon's chorea, which are hypo- and hyperkinetic disorders respectively, arise from degeneration of two intimately connected structures within the basal ganglia, the substantia nigra and the neostriatum. Increasingly, reciprocal connections between different nuclei have been described, suggesting that feedback loops are an integral part of this system. The globus pallidus receives most of its input from the striatum, and the medial part (the entopeduncular nucleus in lower species) is a major source of outflow from the basal ganglia. The afferent and efferent pathways of these nuclei are described. The first part of this thesis describes the anatomical and electrophysiological demonstration of a pathway from the globus pallidus in the rat to the neostriatum. The second part of the thesis discusses the cellular level of organization of the neostriatum. The discovery of histochemical compartmentalization in the striatum, called striosomes and matrix, has suggested an anatomical division of function, corresponding approximately to sensory-motor and limbic functions. The vast majority of cells in the striatum are of a single morphological type, medium sized densely spiny neurons, which receive most of the input, and are the source of output from the striatum. The second part of the thesis describes the development of a technique which has permitted the study of the relationship of the dendrites of these cells to the borders between compartments. Although the striosome/matrix division is defined histochemically, it was found that dendrites of medium spiny cells did not necessarily observe borders. This finding has implications in terms of the roles of these cells in integrating information from the two compartments.