Scientists identify rare brain cells that actively trigger sleep onset

A team of neuroscientists has uncovered evidence that the brain's outer layer plays a more active role in sleep initiation than previously thought. Rather than simply responding to signals from deeper brain structures, the cerebral cortex itself can generate the electrical patterns that usher the brain into slumber.

A Hidden Population#

Researchers at the Albert Einstein College of Medicine identified a class of inhibitory neurons that make up just 1 percent of the cortex's inhibitory cell population—roughly one neuron per thousand cortical cells overall. In studies involving mice, activating these Sst-Chodl neurons was sufficient to trigger sleep. "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," explained Geoffrey Terral, a neuroscientist involved in the work.

Finding the Needle#

The discovery required years of technical refinement. The Sst-Chodl cells are defined by the simultaneous activation of two specific genes. Targeting either gene alone captures a much broader, diverse collection of neurons—far too many to study meaningfully. The research team, led by Renata Batista-Brito, developed a strategy to label cells only when both genes were active simultaneously, making it possible to isolate and manipulate this precise neuronal population.

Rethinking Sleep Control#

The findings, published in Nature, challenge the conventional understanding of sleep neurobiology. For decades, sleep research has operated under the assumption that subcortical—or "deep brain"—regions orchestrate the transition to sleep while the cortex passively follows suit. This work suggests the cortex is far from passive: it can both recognize sleep-associated rhythms and generate them independently. The discovery opens new avenues for understanding how sleep is initiated and could have implications for treating sleep disorders.