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. Author manuscript; available in PMC: 2013 Nov 1.
Published in final edited form as: Prog Neurobiol. 2012 Jul 24;99(2):93–105. doi: 10.1016/j.pneurobio.2012.07.004

Figure 5.

Figure 5

SCN connections to sleep circuits. Several select afferent inputs to the SCN are shown, the photic input via the retina and inputs from raphe nuclei and intergeniculate leaflet (IGL) that appear to have more to do with mediating influences of activity or arousal on the SCN. Many efferents from the SCN terminate in the sub-paraventricular zone (sPVZ) and then converge with direct efferents on cells in the dorsomedial hypothalamus (DMH). Both direct and indirect SCN efferents impact the VLPO, where GABAergic neurons play an important role in inducing sleep. Indirect SCN efferent pathways target the LH where orexin-containing neurons help switch to a state of wake. Cells in the DMH target the LC where noradrenergic (NE) neurons help maintain arousal. Outputs from the SCN indirectly impinge on the VTA to modify reward circuits.