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. Author manuscript; available in PMC: 2020 May 19.
Published in final edited form as: Curr Opin Behav Sci. 2016 Apr;8:78–84. doi: 10.1016/j.cobeha.2016.02.007

Figure 1.

Figure 1

Neural substrates of interval timing and action planning. (Top) An illustration of cortical-basal ganglia and neurotransmitter systems that are the cornerstone for interval timing and action representation. Elements of basal ganglia and cortical networks are respectively highlighted in light blue and red boxes. Multiple functionally-segregated circuits link the cortex and basal ganglia, which enables the control of timing and actions in a context-sensitive manner. The nigrostriatal dopamine pathway connects the substantia nigra pars compacta (SNc) to the dorsal striatum and is part of the motor circuit. The mesocortical dopamine pathway connects the ventral tegmental area (VTA) to the cortex, particularly the frontal lobes. Excitatory (glutamate) and inhibitory (GABA) projections are designated by green and red dashed arrows, respectively. (Bottom) A core system that governs both interval timing and action planning is the medial corticostriatal thalamo-cortical (CSTC) motor circuit, which consists of the SMA and preSMA (red), the striatum (blue), and the thalamus (purple).