How the brain works whilst we sleep: 5 interesting facts

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As there are 24 hours in a day and most people aim for 8 hours sleep a night, the fact that we spend a third of our lives in slumber is an easy statistic to calculate.

However as The Mirror pointed out, it means that the average person in the UK spends a total of 26 years of their life sleeping – so it is surprising that most of us still know very little about what happens to our brains during this time.

Bad sleeping patterns have now been proven to be linked to poor waking cognitive capacity in a new study by researchers at Tel Aviv University’s School of Psychological Sciences. More than that, it is also known that those who sleep less than 6 hours a night have a shorter life expectancy than those who sleep for longer – meaning more general health issues can also occur.

Here we take a closer look at our brains and offer five interesting facts on how they work while we’re in the land of nod.


To an observer, a sleeping person may seem to be in a passive and dormant state but this is far from the case.

The surface of the brain does see activity drop by around 40% in the first phases of sleep but during later stages activity levels go through certain definite stages.

In fact a typical night’s sleep comprises of five separate sleep cycles lasting about 90 minutes each. These cycles are themselves divided into five stages, with the first four being known as ‘quiet sleep’ (or non-rapid eye movement) whilst the final stage is noticeably different due to rapid eye movement (REM) activity.


Activity in the brain can be measured by the type of ‘waves’ it produces at any one time. Alpha waves were the first to be identified and are associated with a calm and restful state.

During the first stage of sleep, brain waves have small undulations. Then, in stage two, there are bursts of activity lasting a couple of seconds which keep the brain in a state of quiet readiness.

Stage three sees brain waves deepen into large, slow waves and this signifies a deep sleep state. Stage four is reached when 50% of the waves are slow. At this point 40% of the usual blood flow to the brain is diverted to the muscles for healing and restoration.


The final stage of the cycle is the deepest sleep state and it is accompanied by rapid eye movement (REM) as the eyes twitch and move. There is also a high level of brain activity.

This is the stage associated with dreaming and sees activity in the pons: the part of the brain stem that relays nerve impulses between the spinal cord and the brain and which sends signals to the thalamus and the cerebral cortex. It also sends signals to turn off motor neurons in the spinal cord, causing temporary paralysis.

The REM stage occurs within 90 minutes of falling asleep and recurs about every 90 minutes throughout the night in the cycle pattern described above.

Although brain activity is high during REM, and we typically spend more than 2 hours each night dreaming, no one really knows what lies behind the mechanisms or even the reasons for the process.

However REM sleep is known to stimulate the brain regions used in learning and so may explain why infants spend much more time in this sleep state than adults.

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When we sleep we are generally in an anabolic state to allow our bodies conserve energy and repair damage. Levels of hormones such as adrenaline and corticosteroids drop and the body starts to produce others in their place.

Melatonin is a hormone produced by the pineal gland located deep inside the brain which helps control body rhythms and sleeping and waking cycles. Levels of melatonin rise as the body temperature falls so encouraging feelings of sleepiness and the opposite happens in order to wake us up.


Humans also have an in built body clock which is known as the circadian rhythm.  A function of the hypothalamus, located at the base of the brain, it causes 24 hour fluctuations in many bodily activities and governs the body’s sleeping and waking cycles.

The circadian rhythm is responsible for far more than just regulating sleep though as everything from digestion to cell renewal takes place on a time schedule which it dictates via a network of chemical messengers and nerve receptors.

Shift work, ‘jet lag’ and insomnia can all disrupt the natural circadian rhythm and have far-reaching negative effects on health as a result.

It is clear that far from being dormant while we sleep, our brains are actually working in a totally different way than in our waking hours and much of what really goes on is still something of a mystery to science. What we do know is that it’s important to give our bodies and brains the best chance of a decent night’s sleep by choosing a supportive and comfortable bed that helps us drift off into our natural sleep rhythms.

supportive-beds-available-from-carpetrightFind plenty of help guides on sleep and on which bed or mattresses to choose in our inspiration and advice section!


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