What happens in the brain when you stay up all night? Unprecedented study in humans reveals synaptic changes
Not getting enough sleep causes more than just tiredness, irritability and the need for caffeine to stay active. New research, published by the scientific journal PLOS Biology, has shown that the absence of sleep for long periods causes noticeable changes inside the brain.
After a period of approximately 28 and a half hours without rest, study participants showed an increase in markers linked to synapses, which are the points of communication between neurons. The brains of those who remained awake revealed signs of a greater number of active connections between nerve cells.
Throughout the day, our mind is constantly active. Every interaction, thought, learning process or stimulus coming from the environment requires an exchange of information between neurons. This communication occurs through synapses, which are small regions where one nerve cell transmits signals to another.
Such connections are fundamental for brain functioning. Thanks to them, we are able to acquire new knowledge, consolidate memories and adjust to different everyday situations. However, keeping all these connections working uninterruptedly requires a lot of energy, generating an overload that impacts the ability to focus, mood and memory.
One of the most accepted theories to explain the importance of sleep is the synaptic homeostasis hypothesis. This theory suggests that during wakefulness, synapses become more robust and numerous as the brain absorbs information. Sleep, then, acts as a period of rebalancing: some vital connections are maintained, while others are adjusted to restore harmony to the neural system.
It is possible to compare this process to a kind of deep organization after an intense day. The brain selects what is essential to preserve and discards what represents “excess” information.
“Sleep is the time for maintenance work that can only be carried out after normal operations have ended: the system is cleaned and metabolic waste is removed. Important memories are archived and unnecessary information is eliminated. Neural connections are adjusted and synapses are strengthened or broken down”, detailed David Elmenhorst, a neuroscientist specializing in sleep at the Jülich Research Center and one of the authors of the research, in an official statement.
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To date, the evidence supporting this hypothesis has mostly come from experiments on animals, such as fruit flies and mice. The new study aimed to observe this mechanism directly in humans.
Details of the research that analyzed the impact of lack of sleep on the brain
The researchers followed a group of 40 healthy adults, with an average age of 28 years. The volunteers were divided into two categories: half had a regular sleep pattern, sleeping around eight hours between exams; the other half remained awake. In the second assessment, this last group had not slept for approximately 28.5 hours.
To visualize the participants’ brains, the scientists employed a combination of magnetic resonance imaging (MRI) and positron emission tomography (PET). The latter is an advanced imaging technique that allows you to monitor processes that occur in real time within the organism.
The team analyzed the levels of a specific protein, known as SV2A, which is present in the structures responsible for releasing neurotransmitters — the chemicals that allow communication between neurons. As this protein has a strong connection with synapses, it serves as an indirect indicator of the number of these connections in brain tissue.
The main finding was that, after the sleep deprivation period, participants exhibited elevated levels of SV2A in several brain areas. Among these regions, the hippocampus, essential for memory formation and learning, and the thalamus, a crucial area for alertness and the processing of sensory information, stood out. The elevation in these markers in such important areas reflects neural overload, indicating a brain that was struggling to maintain mental clarity and the ability to learn.
However, it is essential to emphasize that this increase does not indicate an improvement in brain function due to having more connections. On the contrary, the increase signals that the organ continued to be active for a prolonged time, accumulating a volume of work that would normally be regulated and rebalanced during hours of sleep.
“Our study suggests that sleep deprivation not only causes fatigue, but is also accompanied by measurable changes in neural connections,” concluded the authors in their official statement, reinforcing the importance of rest for brain health.
