Figure 1.

Ascending neuromodulatory pathways. The ascending neuromodulatory systems and their projection nuclei, which send broad projections to different parts of the brain. (a) The cholinergic system, projections from the basal forebrain, including the septal nuclei (top) and basal nucleus of Meynert (bottom); and from the brainstem pedunculopontine/laterodorsal tegmental complex; (b) the noradrenergic system, from the locus coeruleus; (c) the serotonergic system, from the dorsal (top) and median (bottom) raphe nuclei; (d) the dopaminergic system, from the substantia nigra (top) and ventral tegmental area (bottom). (Online version in colour.)