Fig. 1.

Schematic diagram of cholinergic circuits (in red) and their projections within a subset of key brain regions affected in SZ. Cholinergic inputs to prefrontal cortex and hippocampus arise primarily from the basal forebrain group, including the septal cholinergic neurons, the nbM, the preoptic and diagonal band nuclei. Other contributors to the forebrain ACh group are neurons within the substantia innonimata and ventral pallidum. The second major subgroup of ACh-containing neurons, the pontomesencephalic (PM) cholinergic neurons, provides input to brainstem aminergic nuclei (e.g., VTA, SN, and raphe). Cholinergic interneurons intrinsic to the basal ganglia are thought to modulate the relative impact of glutamatergic, dopaminergic, and GABAergic circuits within the ventral striatum. Potential mechanisms of cholinergic regulation of neuronal excitability in prefrontal cortex and hippocampus are also discussed in the text.