Slow brain rhythms do more than reflect sleep—they help trigger it, fruit fly study suggests
· Medical Xpressby Ingrid Fadelli, Medical Xpress
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For most animals, the need for sleep gradually increases during waking hours and then decreases while sleeping. In neuroscience, this accumulating need to sleep is known as sleep pressure.
Understanding how the brain represents the need for sleep could be clinically relevant. For instance, it could help to identify processes that are disrupted in individuals with sleep disorders, such as insomnia and obstructive sleep apnea.
Researchers at the University of Oxford's Center for Neural Circuits and Behavior studied fruit flies to explore the possible contribution of rhythmic changes in neural activity to the regulation of sleep. Their paper, published in Nature Neuroscience, identifies a neural circuit in the fly brain that generates slow electrical oscillations which appear to encode sleep pressure and promote sleep.
"Sleep is one of the great biological mysteries—perhaps the only universal behavior whose function remains unknown," Gero Miesenböck, senior author of the paper, told Medical Xpress.
"For the past 15 years or so, we have been trying to solve this mystery by studying the function of sleep-promoting neurons in the brain. These neurons must somehow 'know' what the molecular substrate of tiredness is and convert it into sleep-inducing electrical activity."
Recording the rhythms of neurons that control sleep
In one of their earlier papers, Miesenböck and his colleagues reported that, in fruit flies, sleep pressure originated in mitochondrial respiration. In simpler terms, this means that a fly's need for sleep is linked to how specific structures inside its cells (i.e., mitochondria) use oxygen to release energy.
As part of their new study, the authors wanted to understand how sleep-promoting neurons in the fly brain respond to different levels of accumulated tiredness.
To do this, they monitored these neurons using a genetically encoded calcium sensor, a protein that changes its fluorescence in response to changes in calcium levels. This is useful because the influx of calcium into neurons can be used as an indicator of their electrical activity.
"The flies were implanted with an optical window (in essence, a drop of transparent glue), and the calcium signals were imaged with a fancy microscope," explained Miesenböck.
"We correlated the optical signals with direct electrophysiological measurements from single neurons and the sleep–wake behavior of the flies. Some experiments simultaneously perturbed the function of the sleep-promoting neurons and/or kept the flies awake overnight to see how the circuit would respond."
The team observed that neurons controlling the flies' sleep generated slow electrical rhythms, alternating between more active and less active states. These rhythms were produced by two distinct groups of neurons located at opposite sides of the fly brain, which took turns in inhibiting each other.
When the researchers disrupted communication between these two groups of neurons, the slow brain rhythms they observed were disrupted and so were the flies' sleeping patterns. The team also successfully recreated the slow activity rhythms using light and found that this prompted flies to sleep.
Shedding new light on how the brain drives sleep
This study offers new insights into how neurons in the brains of fruit flies regulate sleep. Future research could build on these insights and try to determine whether similar mechanisms also promote sleep in other animals, including humans.
"The sleep-promoting circuit we identified oscillates; it produces so-called slow-wave activity that is similar to that in sleeping mammals, including humans," said Miesenböck.
"In humans and other mammals, it has been unclear whether slow-wave activity is causally linked to sleep or merely a byproduct of it. We show that the oscillations have a causal role in flies, and that they are produced by a circuit motif that is typically found in central pattern generators for rhythmic movements."
Miesenböck and his colleagues plan to continue investigating the neural underpinnings of sleep. Their next studies will address other research questions that remain unanswered.
"For instance, is the benefit of sleep directly linked to slow-wave activity? And how is the oscillatory signal converted into binary sleep–wake states?" added Miesenböck.
Written for you by our author Ingrid Fadelli, edited by Sadie Harley, and fact-checked and reviewed by Robert Egan—this article is the result of careful human work. We rely on readers like you to keep independent science journalism alive. If this reporting matters to you, please consider a donation (especially monthly). You'll get an ad-free account as a thank-you.
Publication details
Peter S. Hasenhuetl et al., A half-center oscillator regulates sleep pressure, Nature Neuroscience (2026). DOI: 10.1038/s41593-026-02431-9.
Journal information: Nature Neuroscience
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Ingrid Fadelli
Freelance journalist with BSc Psychology and MA International Journalism. Covers AI, robotics, neuroscience, and astrophysics since 2018. Full profile →
Sadie Harley
BSc Life Sciences & Ecology. Microbiology lab background with pharmaceutical news experience in oil, gas, and renewable industries. Full profile →
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