The doral raphe nuclei, subdivided into different subregions, that may play roles in different types of behavior. It plays a role in arousal states as well as facilitates motor output (Motor neurons are made more excitable/depolarized). Dorsal raphe nucleus activity is also linked sleep/wake cycles. Over 80% of forebrain serotonin comes from the dorsal and median raphe nucleus, making up the rostral serotonin system. The caudal serotonin system projects to the spinal cord.