Cortical cells identified as potential sleep switch

Key facts

• A rare population of cortical cells, Sst-Chodl neurons, can trigger sleep.
• These cells make up about one percent of the cortex's inhibitory neurons.
• Activating these neurons in mice increased slow-wave and REM sleep.
• Stimulating these cells reduced the time mice took to fall asleep.
• The Sst-Chodl neurons have widespread connectivity throughout the brain.
• Researchers are investigating what activates these cells.

Researchers have identified a specific type of neuron in the cerebral cortex that may act as a switch to induce sleep, challenging the long-held belief that sleep is solely controlled by deeper brain regions. The study, published in Nature, focused on Sst-Chodl neurons, which constitute about one percent of the cortex's inhibitory neurons.

These neurons, named after two active genes, possess widespread connectivity, branching out from the visual cortex to areas involved in touch, hearing, memory, navigation, and voluntary movement. Scientists found that activating these Sst-Chodl neurons in mice led to increased slow-wave and REM sleep, reduced the time it took for the animals to fall asleep, and even caused them to seek out their nests during active periods.

While Sst-Chodl neurons are known to be active during periods of accumulated fatigue, the precise mechanism that triggers their activation remains unknown. The researchers are now investigating these cells in other brain regions, such as the prefrontal cortex, to understand their broader role in sleep regulation.