You can only sleep with half of your brain

New research allows us to rethink how we think about sleep and brain activity.

New research allows us to rethink how we think about sleep and brain activity.



Animals aren’t the only creatures that can literally be half asleep. Research shows that the human race can experience this too. A group of researchers from Brown University began to study this phenomenon.

Atlantico: We know that in some animals the brain does not fully rest even when they sleep. Some studies question the existence of this phenomenon in humans. What do we know about it so far?

Bruno Combi: The brain controls all vital functions, including breathing and heart function. Indeed, while we are alive, our brain never fully rests. A completely flat electroencephalogram, or what is called brain death, is almost synonymous with death!

The brain, which is therefore never idle during our lives, however, slows down its activity (more precisely, the frequency of electrical brain waves) at rest and during sleep. This can be observed using an electroencephalograph (EEG), a device that records the electrical vibrations of the brain. As a rule, for the human species, this slowdown of the brain during rest or sleep is bihemispheric in nature. That is, both hemispheres of the brain simultaneously slow down their activity. In other words, the right and left hemispheres of our brain are resting at the same time. It has long been noticed in some animals, in particular in marine mammals, for example, in dolphins, that rest (slowing down of the brain rhythm) of the two hemispheres of the brain in them is not simultaneous, but alternative: rest only applies to one hemisphere of the brain. Then another and vice versa. This phenomenon is also found in some birds and fish.

Read also

Here’s What Actually Causes Sleep Apnea

This is called rest or unihemispheric sleep.

This feature allows the dolphins to continue swimming and remain conscious even while sleeping. And the birds stay awake to avoid a possible predator.

Although the left and right hemispheres of the human brain were known to be largely physically independent of each other, most scientists generally believed that both hemispheres of the brain were resting at the same time.

The Bruno Combi Institute (IBC) empirically observed and suggested for about thirty years as a training method for better sleep control to train people to practice “dolphin sleep” sleep, allowing in practice to remain awake and in conscious visual alertness, in the same way, how dolphins that keep swimming sleep with only one eye at a time (leaving the other open), masking one eye (in humans) and leaving the other open to sleep “with one eye”, then alternating the two sides. In this way, people can learn to sleep better and rest with only one hemisphere of the brain at a time. The optic nerve connecting the eye to the opposite hemisphere of the brain, the resting hemisphere is paradoxically on the same side as the open eye. And the most active hemisphere is on the side of the closed eye. This is a relaxation technique while awake with one eye, called “dolphin sleep”, which can be useful in certain cases (for resting while awake). Thus, it is possible to rest alternately (and not simultaneously) with the two hemispheres of the brain. Some soldiers, lone navigators, or night watchmen use this observation/sleep technique with only one eye (and brain hemisphere) at a time to look more effectively for longer.

Read also

And if we had to draw inspiration from medieval sleep practices to deal with the great post-coronavirus insomnia

Recently, this “single-hemispheric” resting method, which most scientists thought was reserved for certain animals, was scientifically validated in humans using EEG recordings, as explained in this recent Scientific American publication.

How can this behavior be explained in humans?

If the most frequent ordinary sleep in humans is bihemispheric, because today people do not need to remain in active standby mode during sleep. The same cannot be said for dolphins and marine mammals (seals, whales, etc.), which must continue to swim and periodically rise to the surface to breathe. The same for birds, which must ensure the danger of a fox or a possible predator. Consequently, this function is necessarily more developed in some wild animals than in modern man. However, the physical structure of the brain, divided into two hemispheres, is very similar in humans and in these animals. Therefore, there is no reason why this function of unihemispheric rest exists in them, and not in humans. Just because of the laws of evolution, this more useful function for them has been further developed in some animals. But it also exists in humans and we must use it and rediscover it! This function, of course, was very useful to our primate ancestors living in nature (to escape, like birds, from predators), and simply atrophied in modern humans due to lack of stimulation and use. We can rediscover this inherited brain function. Question: What consequences can this rest of only part of the brain have? This little-used function is still present in modern humans and can be stimulated, rediscovered and taught, in particular to develop our mental abilities, as a training for relaxation and mental control, to improve the quality and control of our sleep. It can be useful for each of us at different levels: students to develop their learning abilities and better prepare for exams, soldiers to sleep less and better (while remaining partially awake), athletes to learn to relax better and have more fun. better control of your brain. And each of us to improve self-control, sleep better and be more efficient in all our activities. It is a tool, among other things, for the development of our mental abilities.

What contribution can this knowledge give us?

Just as an athlete learns to perform muscle-building exercises with sometimes only one biceps, then the other, or both, to optimize physical control over their movements, it is useful to use (and train) our brains to rest in bihemispheric or bihemispheric exercises. a unihemispheric mode that allows us to sleep better under all circumstances and with better control to face all the situations that may arise in daily life. This is of course especially useful for those looking for physical or mental performance (athletes, students, athletes of all kinds, chess or go players) and for demanding or night work requiring good sleep/wake control, with little time for sleep or the need to remain on standby at night (lone navigators, air traffic or marine controllers, drivers or night attendants, aircraft, vehicle or train pilots).

The dolphin sleep technique of sleeping with one eye open while resting one hemisphere of the brain at a time is thus a tool, a technique for training oneself to rest better, be in better shape, be more efficient and improve. physical and mental performance.

You can learn to rest better, sleep better (under all circumstances), eat better and live better!

In this way, you will achieve optimal health and better sleep as soon as possible so that you can live better, happier, longer and in great shape!

Bruno Comby is a polytechnic and scientific director of the Bruno Comby Institute:, which conducts research in the field of prevention and promotion of public health.

He is the author of 10 health prevention books, including Eat Better, Live Better, Boost Your Immunity, and Eloge de la sieste (published by TNR). Twenty other articles on sleep by Bruno Comby on the Atlantico website:


Leave a Comment

Your email address will not be published.