Connectivity between GPe and striatum.

<p>Rectangles denote neural populations: D1 and D2 label striatal neurons with D1 and D2 receptors, while PRO and ARK label prototypic and arkypallidal neurons respectively. Arrows and lines ending with circles denote excitatory and inhibitory connections respectively. Black and coloured parts of the circuit highlight the pathways illustrated in each panel. Purple pathways denote routes alternative to those shown in orange. The connections between striatum and GPe are dashed to indicate that it is not known which groups of neurons in striatum and GPe are interconnected–the figure shows only the hypothetical connections discussed in the main text. <b>(A)</b> Part of the indirect pathway connected with movement inhibition. <b>(B)</b> Routes providing evidence for actions to STN. <b>(C)</b> Routes providing normalization to the striatum.