Sleepless night changes the structure of connections in the brain
One night without sleep leads to an increase in markers of synaptic connections between brain cells, which supports the hypothesis that sleep is necessary for restoring cellular balance. This conclusion was reached by scientists led by David Elmenhorst from the Institute of Neuroscience and Medicine (Forschungszentrum Jülich, Germany). Researchers have long been trying to understand the purpose of sleep. One of the leading theories is the synaptic homeostasis hypothesis. Her idea is that during wakefulness, the connections between neurons (synapses) are strengthened, the brain actively processes information, and this requires more energy. As a result, proteins accumulate in the brain, and the load on neural networks increases. It is assumed that sleep reduces these levels, weakens excessive synaptic connections, and restores balance (homeostasis). So far, convincing evidence for this model has been found mainly in animal experiments.
To test whether this mechanism works in humans, the researchers used positron emission tomography (PET) and monitored the level of the synaptic marker SV2A (synaptic vesicular glycoprotein 2A), which serves as an indicator of synapse density. The study involved 40 people; half of them were deprived of sleep for one night.
After about 28 hours of continuous wakefulness, the sleep-deprived group was found to have elevated levels of SV2A in several brain regions at once. Particularly notable changes were recorded in the hippocampus (a region important for memory) and the thalamus (a structure that acts as a relay for information in the brain).
When sleep-deprived participants were allowed a two-hour nap, it was found that higher levels of SV2A correlated with greater expression of slow-wave activity — a marker of deep sleep and the need for it.
Although SV2A is only an indirect measure of synaptic density, and the changes were relatively small, the results support the hypothesis of synaptic homeostasis in humans. They show that the need for sleep is biologically linked to the accumulation of synaptic connections during wakefulness.
As the authors note, sleep deprivation not only causes fatigue, but also leads to measurable changes in neural connections. When the brain remains awake for longer periods, it continues to process stimuli and information, which affects the structure of its networks.
Thus, the study provides important evidence that sleep can indeed reset the brain, helping it to maintain an optimal level of synaptic activity and to keep it working efficiently.
Published
June, 2026
Category
Science
Duration of reading
1-2 min
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Scientific journal PLOS Biology. Article: Learning engages transient and sustained cellular mechanisms in the human brain
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