Monthly Archives: August 2007

Mysteries of the Brain Part – 17 – SLEEPWALKING


This post was written on Thursday, August 09, 2007

A few days back a friend of mine told me that her brother sleepwalks. That got me curious about sleepwalking and its reason. I have also sleepwalked once when I was about fourteen years old- I slept in my room and in the morning I found myself sleeping on my parents’ bed in the adjacent room. I have never sleepwalked after that. In today’s VERITAS we will try to understand this phenomenon.


In medical language sleepwalking is called somnambulism( somn is sleep, ambulism is to move). People are said to sleepwalk when they move around in their sleep or do other actions in their sleep which are normally done by fully awake people. So a sleepwalker may walk around his house while sleeping. Or a sleepwalker may clean the floor or talk or climb stairs during their sleep. Some people have been known to do extremely complicated tasks like driving during their sleep. And there are even cases where murders have been committed during sleepwalking and there is a bizarre case in which a woman had sex with strangers during her sleep! So it is a very complicated behavior!


And sleepwalking is not uncommon at all. About 18% of the population is prone to sleepwalking- i.e. about 1 in 5 people have sleepwalked at least once in their lives! But only 3-6% of the people sleepwalk more than once or twice. Children and adolescents are much more likely to sleepwalk as compared to adults. And males are more likely to sleepwalk than females.


A lot of sleepwalking goes unnoticed because the most common form of somnambulism is not walking in sleep. Most sleepwalkers just get up while sleeping, look around with open eyes, close eyes again and lie down. So people around  such sleepwalkers may never notice.


Most movies depict sleepwalkers as moving around with eyes closed and arms outstretched. But this is not the case. Sleepwalkers move around with their eyes open. They are able to navigate their way using visual clues. It is just that their brain sleeps while their bodies are awake! Sleepwalkers have a blank look in their eyes while they sleepwalk. They can even answer simple questions but they cannot make complex decisions. So there is always a danger that the sleepwalker may hurt himself during sleepwalking. There are cases when sleepwalkers have fallen down stairs or cut themselves while doing complex tasks during sleep.


It is commonly thought that sleepwalkers should not be woken up while sleepwalking. This is not dangerous at all. You can wake up a sleepwalker but he will be extremely surprised. Sleepwalkers never remember what they did during sleepwalking.


Most people think that sleepwalkers are acting out their dreams. But this also is not true. We have seen in an earlier
VERITAS that sleep has various stages( see VERITAS: Mysteries of the Brain part 14, 19th May 2006):


1) stage 1: going from wakefulness to sleep. The EEG shows alpha waves.
2) stage 2:  light sleep. The EEG will show sleep spindles and K complexes.
3) stage 3: deep sleep. The EEG shows theta and delta waves.
4) stage 4 : deepest sleep. The EEG will show delta waves.
5) REM sleep: We dream during this time. The EEG shows alpha and beta waves.


These stages keep repeating during the night.


sleepwalking never occurs during REM sleep. It always occurs during stage 3 and stage 4 sleep. So sleepwalking occurs
during deepest sleep when the person is not dreaming. So the sleepwalker is not acting out his dreams. He is in deep sleep but
a part of his brain tells him to get up and do something complex! And sometimes the person will not go back to bed unless he has
completed his task! So a person who wants to clean a table will not go back till he has cleaned it all. And repeated attempts to take him
back to bed would be futile because he will keep getting up to finish his task. Also since the first 3rd and 4th stage of sleep occurs
after about 90 minutes of our going to bed so most sleepwalking occurs about 90 minutes after the person goes to bed.


Very little is known about the exact reasons for sleepwalking. During some laboratory experiments it was found that the primitive
sections of the brain showed lots of electrical activity while the higher logical brain such as the neo-cortex was completely devoid
of electrical signals. This shows that the limbic system was in charge of the body’s movements during this time. The logical or
the higher brain(neo-cortex) was sleeping while the body was moving. But remember: the limbic system is also the emotional centre of the
brain. So sleepwalking must have a emotional content.  And that explains why sleepwalking mostly affects people with some emotional
stress. And that is why lots of teenagers show more sleepwalking than adults.


But I don’t think we have explained sleepwalking fully. It is still a mystery of the human brain. Finding answers will need a lot
of research.


Our life is twofold; sleep hath its own world,
A boundary between the things misnamed
Death and existence: sleep hath its own world,
And a wide realm of wild reality,
And dreams in their development have breath,
And tears, and tortures, and the touch of joy;
They leave a weight upon our waking thoughts,
They take a weight from off our waking toils,
They do divide our being; they become
A portion of ourselves as of our time,
And look like heralds of eternity;
They pass like spirits of the past,–they speak
Like sibyls of the future; they have power,–
The tyranny of pleasure and of pain;
They make us what we were not,–what they will,
And shake us with the vision that’s gone by.
( Lord Byron)





Go, wondrous creature! mount where Science guides:
Go, measure earth, weigh air, and state the tides:
Instruct the planets in what orbs to run,
Correct old time and regulate the Sun;