Insomnia and long-term sleep deprivation have many negative effects on health, which has been repeatedly supported by a lot of scientific evidence. But what might an occasional all-nighter, such as before an exam, do to the brain? A new study shows that short periods of acute sleep deprivation can produce potent antidepressant effects that last for days.
This research was published in Neuron, an authoritative journal in the field of neuroscience. The corresponding author of the paper is Professor Yevgenia Kozorovitskiy of Northwestern University. Like many people, she has had the experience of staying up all night, and was deeply impressed by the "physically exhausted and mentally excited" state after staying up late.
In order to explore how the brain may be affected during this process, the research team designed an animal experiment to gently disturb the sleep of mice and allow healthy mice to experience a "sleepless day" - after all, mice sleep during the day. The habit of coming out at night is just opposite to that of humans.
Through a series of behavioral tests, the researchers found that compared with the normal sleep control group, male mice with acute sleep deprivation became more hyperactive, more aggressive toward mice of the same sex, and had enhanced sexual behavior with mice of the opposite sex. , and depressive-like behavior decreases when faced with certain situations of learned helplessness.
At the same time, using cutting-edge technologies such as optogenetics and genetically encoded chemical genetics, researchers detected the activity of dopamine neurons in the mouse brain, because these neurons regulate sleep stages through the release of dopamine and are related to emotional states. related to the transformation. The results showed that after a temporary lack of sleep, the activity of dopamine neurons increased.
In the four brain regions responsible for dopamine release—the prefrontal cortex, nucleus accumbens, hypothalamus, and dorsal striatum—the researchers observed increased dopamine release after acute sleep loss in all three brain regions. Further analysis found that the increase in dopamine release in these brain areas corresponded to different behavioral performances of the mice. Among them, the dopamine response in the prefrontal cortex was most obviously related to the reduction of depressive-like behavior; the other two brain areas were more closely related to hyperactive behavior. Related. "This means that the prefrontal cortex is a clinically relevant region when looking for therapeutic targets for depression," the researchers noted.
It is worth noting that behavioral manifestations such as hyperactivity and increased social interaction will soon "calm down" a few hours after acute sleep deprivation, but the antidepressant effect can last for several days. This means that the connections between neurons in the prefrontal cortex, known as synaptic plasticity, are likely to have changed.
The researchers then conducted a detailed examination of individual neurons in the prefrontal cortex, and sure enough, they discovered the signature feature of synaptic plasticity on the dendritic structure of the neurons: the formation of more tiny protrusions - dendritic spines.
Therefore, the results of this series of experiments indicate that after acute sleep loss, dopamine release in the brain increases and the plasticity of neural connections in specific brain areas strengthens, allowing animals to maintain a higher mood in response to stress in the following days. . In other words, acute sleep deprivation induced significant antidepressant effects.
Why just one day of sleep deprivation fundamentally changes the brain? The researchers admit that this is still a mystery, but they speculate that this high degree of vigilance in the brain may have been developed during evolution. "It's clear that acute sleep deprivation activates organisms to some extent," explains Professor Kozorovitskiy. "You can imagine that in a situation where you're facing a predator or some kind of danger, you would need to combine the ability to postpone sleep with a relatively high functions combined.”
Although experimental results show that occasionally staying up late can increase antidepressant mood, the study authors caution that people should not stay up late specifically to overcome depression. After all, the antidepressant effect obtained at the expense of sleep is short-lived, and the chronic effects of staying up late are very harmful.