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. Author manuscript; available in PMC: 2013 Jul 1.
Published in final edited form as: Physiol Rev. 2012 Jul;92(3):1087–1187. doi: 10.1152/physrev.00032.2011

FIGURE 5.

FIGURE 5

Dorsal and ventral pathways of the ascending reticular activating system (ARAS). The dorsal pathway (blue) originates in pontine and midbrain reticular formation, most prominently cholinergic (LDT/PPT) and glutamatergic neurons which project to the “nonspecific” intralaminar and midline thalamic nuclei which diffusely innervate many areas of the cerebral cortex as well as thalamic relay neurons with more selective projections patterns. The ventral pathway also originates in pontine/midbrain regions and projects to the lateral hypothalamic (LH) and tuberomammillary (TMN) nuclei of the hypothalamus, as well as the basal forebrain (BF). Output of LH and TMN also ascend to BF, which in turn projects to the cortex. Noradrenergic neurons of the locus coeruleus (LC) and serotonergic neurons in the dorsal raphe (DR) contribute to both pathways and send direct projections to the cortex as do histamine neurons of the TMN and orexinergic neurons in the LH. LDT, laterodorsal tegmental nucleus; PPT, pedunculopontine nucleus. [Adapted from Paxinos and Watson (989), with permission from Elsevier.]