Figure 6.

Dopaminergic control over information accumulation and action. Different classes of dopaminergic receptors—the excitatory (G_s) D₁R and the inhibitory (G_i) D₂R—are preferentially expressed on different cells in both the striatum (Str) and cerebral cortex (the large trapezoidal structure). The distribution of these receptors is such that the presence (or absence) of dopamine—the putative control parameter of this process—likely facilitates a demarcation between two distinct information processing stages: at high levels of dopamine, such as when an animal is motivated, D₁R augment firing in L5_IT pyramidal cells (red and green neurons, depicting a hypothetical choice between two options: red and green) and direct pathway striatal neurons. The dopaminergically excited striatal neurons ultimately disinhibit (via the globus pallidus internus; GPi) diffusely projecting, matrix thalamic nuclei in the ventral tier of the thalamus (Thal; orange; [56,131]), which in turn innervate the supragranular regions of the cerebral cortex and help transition D₂R-enriched L5_PT pyramidal cells into a burst-firing mode (via apical Ca²⁺ waves; [79]) that triggers actions (via subcortical projections), while also innervating the indirect pathway of the basal ganglia (which is typically inhibited by the presence of dopamine via D₂Rs). This action ultimately cancels the thalamic disinhibition mediated by the direct pathway via inhibitory connections in the globus pallidus externus (GPe) and hence effectively signals the end of an information accumulation epoch.