What happens in a sleepwalker's brain? Scientists explain

Are you or do you know someone who sleepwalks? This abnormal sleep behavior — popularly known as “sleep-walking ” and scientifically as “parasomnia ” — is a disorder that occurs due to a change in the normal functioning of the brain. In it, despite being asleep, the person can perform motor activities, such as sitting in bed, walking and talking.

Sleepwalking is most common among children, but it can also affect about 2 to 3 percent of adults, according to sleep researchers. To better understand what happens in the brain during sleepwalking episodes researchers from the Dutch Institute of Neurosciences conducted a new study, published on the 9th in the scientific journal Nature Communications.

“It was commonly believed that dreams only occurred in one stage of sleep: REM sleep. Now we know that dreams can also happen at other stages. Those who experience parasomnias during non-REM sleep sometimes report having dream-like experiences and sometimes appear completely unconscious (i.e. on autopilot),” explains Francesca Siclari, head of the dream laboratory where the study was conducted, in a press release.

REM sleep is considered the deepest stage of sleep, characterized by temporary paralysis of the body's muscles, which allows complete relaxation, and rapid eye movements. According to the Brazilian Sleep Association, mental activity during REM sleep is associated with our dreams. Non-REM sleep is made up of three stages, from superficial to deepest.

How was the study carried out?

Researchers investigated the experiences and brain activity patterns of patients with parasomnia in non-REM sleep. To carry out this type of analysis, the patient must fall asleep, experience an episode of sleepwalking and have their brain activity recorded.

“There are currently few studies that have managed to overcome this. But with the different electrodes we use in the laboratory and some specific analysis techniques, we can now obtain a very clean signal, even when patients move,” explains Siclari.

To carry out the study, the researchers needed to provoke an episode of sleepwalking in the laboratory. For this, two recordings were necessary: ​​in the first, the patient sleeps normally, followed by a night in which he must remain awake and only sleep the next morning.

During the second recording, the patient is exposed to loud sound as they enter the deep sleep phase. In some cases, this can result in an episode of sleepwalking. After this episode, the researchers asked the patient what was going through his mind.

In 56% of episodes, patients reported that they were dreaming while sleepwalking . “Often it was about misfortune or imminent danger. Some reported that they thought the ceiling would collapse. One patient thought she had lost her baby and was searching through the sheets and got up on the bed to try to prevent ladybugs from sliding down the wall and dying,” explains Siclari.

The researcher also says that in 19% of cases, patients said they did not experience anything specific, but woke up making movements as if they were in a trance. A small proportion of participants reported that they had experienced something, but could not remember what it was.

Based on these results, the researchers were able to compare the measured brain activities and find parallels. According to Siclari, patients who dreamed during the episode had brain activations similar to those that occur in the deepest stage of sleep, as if they were dreaming — both immediately before the episode and during the episode — compared to patients who did not. experienced nothing.

The researcher explains that what determines whether the patient will be completely unconscious or whether they will dream may depend on the state the patient is in at the time of the episode. “If we activate the brain while they are probably already dreaming, they seem to be able to 'do something' with the activation, whereas when the brain is largely 'inactivated,' simple behaviors seem to occur without experience,” she explains.

The next steps

The researcher states that the results of the current study are just the first step towards understanding what happens to the brain during an episode of sleepwalking. Therefore, more studies still need to be carried out.

Despite this, Siclari is confident that his work can provide valuable information for developing drugs to treat the sleep disorder. “Parasomnias are often treated with nonspecific sleep medications, which are not always effective and can have negative side effects. If we can deduce which neural system is functioning abnormally, we could eventually try to develop more specific treatments,” she says.