Scientists Find a Potential “Sleep Switch” in the Brain

Activating a small population of inhibitory neurons throughout the cerebral cortex increased slow-wave and REM sleep in freely moving mice. The treatment also reduced the time the mice needed to fall asleep and allowed them to build nests during the day.

The researchers then activated the neurons during the dark period, when nocturnal mice are normally awake. The mice slept more during their usual waking hours than they otherwise would.

“You can get them to sleep more during their waking hours than they would normally sleep during the day,” Battista-Brito says. “We didn’t think this experiment would work. We’re manipulating 1 percent of inhibitory neurons with local injections, so we’re only attacking a portion of those cells. And we saw some really surprising effects.”

Sst-Chodl neurons may sense sleep pressure

The findings suggest that Sst-Chodl neurons could act as sleep-pressure sensors in the cerebral cortex. The idea was first proposed by Thomas Kilduff, director of SRI International’s Center for Neuroscience and a co-author of the study.

Sleep is regulated by two major processes. The circadian process follows the body’s internal clock and the light-dark cycle, while homeostatic sleep pressure builds up with accumulated fatigue and eventually makes a person—or an animal—fall asleep. Kilduff showed that these neurons are most active in the cortex after sleep deprivation, Battista-Brito says.

However, researchers still do not know what naturally activates these cells.

What activates the brain’s potential sleep switch?

“What’s important to note about our study is that it was done in the visual cortex,” Battista-Brito says.

The researchers believe the regulatory role of Sst-Chodl neurons may extend to other brain regions, although the neural wiring may differ. Battista-Brito’s lab is repeating the anatomical part of the study in the prefrontal cortex.

The researchers predict that the prefrontal cortex will receive input from regions including the hypothalamus and thalamus. These connections could specifically activate neural networks involved in sleep.

The study argues that these cells are conserved from salamanders to humans, raising the possibility that they could help explain sleep disorders associated with many mental illnesses.

Three questions remain

The researchers are now investigating three key questions: what activates Sst-Chodl neurons, whether the cells truly sense sleep pressure, and why they increase delta-wave activity.

Nature, 2026. DOI: 10.1038/s41586-026-10876-y