Why does the need for sleep become stronger the longer we stay awake? Researchers studying mice have identified two groups of brain cells that may help explain how the body builds sleep pressure.
Scientists from the University of Basel, Beth Israel Deaconess Medical Center and Auburn University examined brain activity during normal sleep and wake periods as well as after extended sleep deprivation.
Neurons Track Time Awake
The researchers identified two groups of brainstem neurons: GABAergic and serotonergic neurons. Their activity increased as the animals remained awake for longer periods and decreased after sleep began.
This pattern suggests that the cells may respond not simply to being awake, but to the amount of time spent awake.
Testing the Connection
Researchers then changed the activity of the neurons. Activating them caused the mice to sleep longer and more deeply, resembling recovery sleep after prolonged wakefulness.
When the neurons were inhibited, the animals slept considerably less. In experiments involving both groups, sleep was reduced by about 70%.
A New View of Sleep Pressure
The findings suggest that some brain cells may do more than monitor prolonged wakefulness. They could help turn time spent awake into an increasing biological demand for sleep.
The research may eventually contribute to a better understanding of sleep disorders and prolonged sleep loss. However, the experiments were conducted in mice, so they do not yet establish that the same mechanism works identically in humans.