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. Author manuscript; available in PMC: 2010 Apr 12.
Published in final edited form as: Behav Brain Res. 2008 Oct 4;199(1):141–156. doi: 10.1016/j.bbr.2008.09.029

Figure 1.

Figure 1

Left. Functional anatomy of the basal ganglia circuit, showing an updated model of the primary projections. In addition to the classic “direct” and “indirect” pathways from Striatum to BG output nuclei originating in striatonigral (Go) and striatopallidal (NoGo) cells respectively, the revised architecture features focused projections from NoGo units to GPe and strong top-down projections from cortex to thalamus. Further, the STN is incorporated as part of a newly discovered hyperdirect pathway (rather than part of the indirect pathway as originally conceived), receiving inputs from frontal cortex and projecting directly to both GPe and GPi. Right. Neural network model of this circuit, with four different responses represented by four columns of motor units, four columns each of Go and NoGo units within Striatum, and corresponding columns within GPi, GPe and Thalamus. Fast spiking GABA-ergic interneurons (γ-IN) regulate Striatal activity via inhibitory projections. For implementational details, see Frank (2005, 2006).