Date of Award
Doctor of Philosophy
The structural and neurochemical organization of the basal ganglia of the rat was investigated with highly sensitive modern anterograde and retrograde tracing methods in combination with immunocytochemical identification of intrinsic neuronal substances with the optical and laser-confocal microscope to address the fundamental organization of these centers as an integrated system.;Based on the present results and other evidence, a functional model of the basal ganglia is proposed: The corticostriatal inputs activate a large population of striatal neurons. Among these, appropriate neurons are 'selected' within each functional domain by the dopaminergic, cholinergic, and GABAergic recurrent collateral inputs. The same corticostriatal input simultaneously activates type II spiny projection neurons from each functional domain, which inhibit a population of parvalbumin-containing GABAergic pallidal neurons. These pallidal neurons disinhibit a number of pallidostriatal neurons via axon collaterals. The appropriate population of pallidostriatal neurons is 'selected', probably by subthalamic afferents. The selected GABAergic pallidostriatal neurons then inhibit striatal functional domains, thereby 'selecting' only the appropriate functional unit. The selected population of striatal projection neurons then inhibits a number of GABAergic neurons of the basal ganglia output centers. Again, appropriate neurons are 'selected' by subthalamic afferents and recurrent collaterals. The selected GABAergic neurons then disinhibit the thalamus, pedunculopontine nucleus and/or the superior colliculus via axon collaterals. The information sent to the thalamus is used to program memory, whereas that directed to the pedunculopontine nucleus or the superior colliculus participates in motor execution. The dorsolateral striatal circuit operates during sensory-guided and self-paced movements, while the medial and ventral striatal circuit operates during memory-guided movements. Striatal interneurons, globus pallidus neurons, subthalamic nuclear neurons and dopaminergic neurons play a role in 'selecting' the appropriate sets of neurons at different levels. (Abstract shortened by UMI.)
Rajakumar, Nagalingam, "Neuroanatomical And Neurochemical Organization Of Compartments In The Basal Ganglia Of The Rat" (1993). Digitized Theses. 2278.