For a long time, sleep research has treated the cerebral cortex as a passive follower reacting to signals from the deep brain. The cortex is where the slow rhythms of deep sleep can be seen, but researchers assumed the signals that triggered them originated elsewhere. In a recent Nature study, Terral and Renata Batista-Brito, who runs the lab, report a population of cortical cells that challenges that assumption.
These cortical cells make up only around one percent of the cortex’s inhibitory neurons, and switching them on in a mouse puts the animal to sleep. The cells are called Sst-Chodl neurons, after two genes that are active in them. Long-range inhibitory neurons marked by the activity of these genes have been known for some time, based on studies in monkeys, but researchers couldn’t figure out how to manipulate them using these genes.
Aiming at either one of these genes captures a huge, heterogeneous family of different neurons. Inhibitory neurons account for about a fifth of all cortical neurons, so Sst-Chodl cells amount to roughly one neuron in a thousand in the cortex. Building a strategy that labels a cell only when both genes are on took her team years.
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