Nodding off in a dull class? Blame the neurons

The irresistible urge to sleep when bored can be blamed on neurons in the brain’s pleasure centre.

Sleep is controlled by our internal biological clock and the length of time we’ve already spent awake or asleep. Emotions and brain activity can also trigger sleep at other times, but the neural circuitry behind this effect is unknown.

A team including researchers from the University of Tsukuba pinpointed neurons in the nucleus accumbens — a brain area associated with reward and motivation — that respond to adenosine, a chemical produced in the body that promotes sleep. They used light and chemical stimulation to selectively activate these neurons in mice, which consequently fell into a deep sleep. However, exciting sleep-deprived mice with toys and chocolate suppressed the same neurons and prevented the onset of sleep.

Drugs that target these neurons could help treat insomnia and other sleep disorders.