Psychopharmacology of wakefulness: pathways and neurotransmitters.

aMonoaminergic projections from brainstem to cortex via the ascending reticular activating system are illustrated here. Perhaps one form of arousal is a stimulated type of external vigilance, with tense hyperarousal, putting the individual on the lookout for threats from the environment. This type of arousal may be mediated by the monoamines dopamine, norepinephrine, serotonin, and acetylcholine via their ascending projections from the brainstem as part of the classical reticular activating system. The ability to activate this system enhances the survival of an individual in a hostile environment. Stimulants such as amphetamine and caffeine activate this system. Figure 1. Stimulated Vigilance Psychopharmacology of Wakefulness: Pathways and Neurotransmitters