According to Stanford University researchers, a primary circuit in the brain's reward involving the chemical "feel-good" chemical dopamine, is also essential for controlling our sleep-wake cycles.
“Insomnia, a multibillion-dollar market for pharmaceutical companies, has traditionally been treated with drugs such as benzodiazepines that nonspecifically shut down the entire brain," says psychiatry and behavior science professor Luis de Lecea "Now we see the possibility of developing therapies that, by narrowly targeting this newly identified circuit, could induce much higher-quality sleep.”
It makes intuitive sense that the reward system, which motivates goal-directed behaviors such as fleeing from predators or looking for food, and our sleep-wake cycle would coordinate with one another at some point. You can’t seek food in your sleep, unless you’re an adept sleepwalker. Conversely, getting out of bed is a lot easier when you’re excited about the day ahead of you...
The reward system’s circuitry is similar in all vertebrates, from fish, frogs and falcons to fishermen and fashion models. A chemical called dopamine plays a crucial role in firing up this circuitry.
Neuroscientists know that a particular brain structure, the ventral tegmental area, or VTA, is the origin of numerous dopamine-secreting nerve fibers that run in discrete tracts to many different parts of the brain. A plurality of these fibers go to the nucleus accumbens, a forebrain structure particularly implicated in generating feelings of pleasure in anticipation of, or response to, obtaining a desired objective.
“Since many reward-circuit-activating drugs such as amphetamines that work by stimulating dopamine secretion also keep users awake, it’s natural to ask if dopamine plays a key role in the sleep-wake cycle as well as in reward,” Eban-Rothschild said.