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. Author manuscript; available in PMC: 2011 Dec 1.
Published in final edited form as: Curr Opin Neurobiol. 2010 Sep 7;20(6):717–725. doi: 10.1016/j.conb.2010.08.008

Figure 1.

Figure 1

Schematic diagrams of the basal ganglia-superior colliculus circuit. (A) Classical model of the basal ganglia - superior colliculus pathway. (B) Updated model in light of new evidence (not complete). As the only glutamatergic projection in the basal ganglia, the subthalamic nucleus can act to prevent a saccade by activating the nigra. This is the indirect pathway. By inhibiting the nigra, the striatum can cause disinhibition of the colliculus, thus activating a saccade. Newly revealed projections from the colliculus to the subthalamic nucleus and to the dopaminergic neuron containing pars compacta and ventral tegmental area, suggest a need to revise theories related to these areas. Red lines terminating in filled circles denote inhibitory projections. Black lines ending in inverted arrowheads denote excitatory projections. Green lines terminating in filled circles denote dopaminergic projections. Abbreviations: GPe = Globus Pallidus external; STN = subthalamic nucleus; nigra = subtantia nigra pars reticulata; compacta = subtsantia nigra pars compacta.