Sleepwalking is one of the most fascinating and mysterious sleep disorders. While many of us think of sleep as a time for the brain to rest and rejuvenate, the reality is that the brain is still incredibly active during sleep. In the case of sleepwalking, the brain sends mixed signals, causing the body to move and act as though it’s awake, while the person is still in a state of unconsciousness.
But what exactly happens in the brain during sleepwalking?
How does the brain manage to control the body without full consciousness?
In this article, we’ll dive into the neurological side of sleepwalking and explore what’s going on behind the scenes when someone takes those midnight strolls without remembering a thing.
The Sleep Cycle and Sleepwalking
To understand what happens in the brain during sleepwalking, it’s important to first have a basic understanding of the sleep cycle. Sleep is divided into two major stages: non-rapid eye movement (NREM) sleep and rapid eye movement (REM) sleep. NREM sleep itself is broken down into three stages, with NREM Stage 3 being the deepest.
Sleepwalking typically occurs during NREM Stage 3, also known as slow-wave sleep (SWS). This is the deepest stage of sleep, where the brain’s activity is slowed down, the heart rate and breathing decrease, and the body is at its most relaxed. Sleepwalking occurs when there’s a partial arousal from this deep sleep stage—meaning that certain areas of the brain wake up, but not enough to achieve full consciousness.
Neurological Explanation: What Happens in the Brain?
When a person sleepwalks, several areas of the brain function in an unusual manner. Here’s how the brain works during a sleepwalking episode:
The Sleep-Wake System Misfires
- Sleepwalking occurs when the brain’s sleep-wake system experiences a mix-up. Normally, during deep sleep, the reticular activating system (RAS), which regulates wakefulness, is turned off. However, during sleepwalking, the RAS is partially activated, leading to physical activity while the person remains unconscious. This activation allows the body to perform movements, even though the individual is still in a deep sleep state.
Inhibited Prefrontal Cortex
- One of the main areas of the brain responsible for higher-level decision-making and reasoning is the prefrontal cortex. During sleepwalking, this part of the brain remains largely inactive, meaning the sleepwalker is not fully conscious and lacks the cognitive functions necessary to make rational decisions. This is why sleepwalkers can engage in complex behaviors like walking or talking but have no memory or awareness of their actions.
Active Motor Cortex
- The motor cortex, which controls voluntary muscle movement, remains active during sleepwalking. This part of the brain is responsible for sending signals to the body to perform actions, such as walking, sitting up, or even opening doors. Despite the motor cortex being active, the lack of awareness from the prefrontal cortex leaves the person completely unaware of their actions during the episode.
Increased Brain Connectivity
- Sleepwalking episodes have been shown to occur due to increased connectivity between brain areas that regulate motion and the arousal system. A study published by the National Center for Biotechnology Information (NCBI) suggests that certain parts of the brain involved in movement remain more connected during sleepwalking, causing a state of motor activation despite the brain being in deep sleep.
You can read more about the study here.
The Role of Genetics and Triggers
Sleepwalking is more common in people who have a family history of the disorder, suggesting a genetic predisposition. This means that the brain structure and sleep patterns that make sleepwalking more likely can be passed down through generations.
Aside from genetics, certain triggers can increase the likelihood of a sleepwalking episode.
These include:
- Sleep deprivation
- Stress and anxiety
- Alcohol consumption
- Fever or illness
- Certain medications
When these factors disturb the brain’s sleep architecture, it increases the chance of partial arousal during slow-wave sleep, setting the stage for sleepwalking.
Why Don’t Sleepwalkers Remember Anything?
One of the most perplexing aspects of sleepwalking is the lack of memory or awareness during and after an episode. This can be explained by the brain’s state of consciousness during the event. The areas of the brain responsible for memory encoding, such as the hippocampus, are largely inactive during sleepwalking. Since memory formation is impaired, sleepwalkers rarely have any recollection of their actions upon waking.
Sleepwalking and the Fight-or-Flight Response
Interestingly, sleepwalking episodes can sometimes be triggered by the fight-or-flight response—a survival mechanism that kicks in during stressful situations. During sleep, the amygdala, the brain’s emotional center, can become activated, especially in response to stress or anxiety. This activation can result in a partial arousal from deep sleep, causing the sleepwalking episode. The person may appear anxious or even distressed during the episode, which is consistent with the heightened arousal from the fight-or-flight response.
Can Sleepwalking Be Dangerous?
While most sleepwalking episodes are harmless, they can sometimes lead to dangerous situations. Sleepwalkers can trip, fall, or engage in risky behaviors like leaving the house or operating machinery without being aware of their surroundings. In rare cases, sleepwalkers have exhibited violent behavior during episodes, which can pose a risk to themselves or others.
If sleepwalking becomes frequent or hazardous, it may be a sign of a deeper sleep disorder, such as nightmare disorder or REM sleep behavior disorder. In such cases, it’s important to seek professional medical advice for further evaluation and treatment.
Sleepwalking is a complex behavior that occurs when the brain is partially awake but remains largely unconscious. The unique combination of an active motor cortex and inactive prefrontal cortex allows the body to move without the person being aware of it.
Stress, sleep deprivation, and genetic factors all contribute to the likelihood of experiencing sleepwalking episodes. Understanding the neurological side of sleepwalking helps us see why it happens and why people often have no memory of their actions.
If sleepwalking is becoming a frequent or dangerous occurrence, it’s important to consult with a sleep specialist who can offer treatment options, such as cognitive behavioral therapy (CBT) or medication, to help manage the condition.
