During sleep deprivation, the brain remains awake longer and continues to process stimuli and information. The study shows that after approximately 28.5 hours of wakefulness, a marker for synaptic density increases in several brain regions. This suggests that sleep deprivation not only causes fatigue but is also accompanied by measurable changes in neural connections.
A Night Without Sleep Alters Synaptic Density in the Brain
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23 June 2026
What happens in the brain when people stay awake all night? A new PET/MRI study by researchers at the Forschungszentrum Jülich involving 40 healthy adults provides one of the most direct indications to date in humans: After approximately 28.5 hours of wakefulness, a marker of synaptic density was elevated in several brain regions. Synapses are the contact points through which nerve cells exchange information. The finding supports the assumption that sleep is not just rest, but helps the brain restore balance to its neural connections.
Why Sleep Is More Than Just a Break
In everyday life, sleep is often viewed as wasted time. However, the study from the “Molecular Organization of the Brain” research division at the Institute of Neuroscience and Medicine at Forschungszentrum Jülich shows that sleep deprivation does more than just make you tired. It is accompanied by measurable changes in a central biological system of the brain: the synapses.
Synapses are the junctions between nerve cells. They change when we learn, think, process stimuli, or concentrate. Being awake therefore means work for the brain: it takes in information, evaluates it, and adjusts connections. Sleep could help restore balance to these neural connections.
How the study was conducted
The study examined 40 healthy adults with an average age of around 28. The participants were randomly divided into two groups. A control group slept an average of 7.8 hours between measurements. The other group stayed awake; at the time of the second examination, these individuals had gone an average of 28.5 hours without sleep.
Measurements were taken twice in the morning using a combination of PET and MRI. The researchers used the PET tracer F-18 SynVesT-1, which binds to SV2A. Synaptic vesicle glycoprotein 2A (SV2A) is located in the membrane of synaptic vesicles—the tiny bubble-like structures in nerve endings that store and release neurotransmitters—and helps regulate how these chemical messengers are packaged and released at the junctions between brain cells. SV2A is an established marker for indirectly estimating synaptic density in the living brain.
What really surprised me is the extent of the changes in synaptic density caused by just a single night without sleep.
Interview with David Elmenhorst on the Significance of the Research Findings
What the researchers found
Following sleep deprivation, a significant increase in this marker was observed in most of the brain regions studied, suggesting higher synaptic density. This increase was associated with an increase in deep sleep activity during restorative sleep.
Highlighted in the abstract: | |
Brain region | Change after sleep deprivation |
Hippocampus | +5,6 % |
Thalamus | +4,6 % |
Parietal cortex | +3,2 % |
The hippocampus is important for learning and memory. The thalamus plays a central role in wakefulness and stimulus transmission. The parietal cortex is involved in attention and spatial orientation, among other things.
The findings provide one of the most direct indications to date in humans that sleep deprivation shifts the brain’s synaptic balance. Furthermore, the results may also help to better understand normal physiological fluctuations in synaptic density.
This is important for medicine. In research on mental illnesses—such as depression—changes in synaptic structure are increasingly being discussed as a possible biological factor. However, such differences can only be meaningfully interpreted if it is clearer how much synaptic markers fluctuate even in healthy people: due to sleep, wakefulness, time of day, stress, or rest.
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FAQ: Sleep Deprivation, the Brain, and Synaptic Density
1. What happens in the brain during sleep deprivation?
2. Is a night without sleep harmful to the brain?
3. What is synaptic density, simply explained?
4. Why does the brain need sleep?
5. Why is this sleep study scientifically important?
6. Is sleep deprivation linked to depression?
7. Can sleep influence mood?
8. What is SV2A?
9. Can sleep deprivation trigger mental illnesses?
10. Can chronic sleep deprivation cause lasting damage to the brain?
Original Publication
David Elmenhorst ,Anna L. Foerges,Ali Gordji-Nejad,Eva-Maria Elmenhorst,Tina Kroll,Andreas Matusch,Simone Beer,Bernd Neumaier,Philipp Krapf,Christoph Lerche,Alexander Drzezga,Andreas Bauer, Sleep deprivation increases levels of the synaptic density marker SV2A in the human brain, DOI: https://doi.org/10.1371/journal.pbio.3003816
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Prof. Dr. med. David Elmenhorst
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Last Modified: 30.06.2026