Researchers at the Albert Einstein College of Medicine have identified a population of cortical cells in mice that can independently initiate sleep. For a long time, sleep research assumed the cerebral cortex passively reacted to signals originating in deeper brain regions. This new study challenges that assumption, demonstrating the cortex’s ability to both perceive and generate the slow rhythms associated with deep sleep.
Geoffrey Terral, a neuroscientist at the Albert Einstein College of Medicine in New York, explained that traditionally, “sleep is associated with being controlled by subcortical regions.” The study, published in *Nature*, focused on cells called Sst-Chodl neurons, which comprise approximately one percent of the cortex’s inhibitory neurons. Activating these cells in mice induced sleep, indicating they are sufficient to promote the state.
Renata Batista-Brito, who runs the lab, detailed the difficulty in isolating these specific neurons. Targeting either of the genes individually, Sst or Chodl, would capture a large and varied group of cells. “A single gene is not able to target these cells,” she said. The team spent years developing a method to label cells only when both genes were active, as inhibitory neurons make up about a fifth of all cortical neurons, meaning Sst-Chodl cells represent roughly one neuron in a thousand. Batista-Brito emphasized the importance of specificity, stating, “If you’re not really specific, the contaminants are going to be much more dominant than the specific cells.”
Terral stated, “What our work shows is that the cortex can not only see this rhythm but also initiate it by itself, and this is sufficient to promote sleep,” suggesting a more active role for the cortex in sleep regulation than previously understood.
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