Why can t some people fall asleep in an unfamiliar environment?

Mondo Health Updated on 2024-01-28

Introduction: The brain will have some different sleep states than usual, and the left brain will be in a lighter sleep at this time, so that the person who recognizes the bed will be more alert, which may have a similar meaning to the unilateral brain sleep of some marine mammals and birds. What is the meaning of asking?This may be a "vigil" skill left by the ancestors.

Last week, the senior sister suffered from insomnia, tossing and turning, and it was difficult to sleep peacefully, because it was the first day of a business trip, and the senior sister boiled it down to two words - recognize the bed!In a daze, the middle school sister thought, is there any scientific reason for recognizing the bed?In fact, in human sleep research, not sleeping well in a new environment is considered a typical sleep disorder, known as the first night effect. At this time, the brain will alert one hemisphere more than the other to watch the surrounding environment, and if it detects an unfamiliar external signal, it will immediately wake up the sleeping human.

Speaking of which, the senior sister thought of dolphins. Falling asleep and being awake were once thought to be two mutually exclusive states, but it has now been established that aquatic mammals, birds, and possibly even reptiles can sleep with one eye open and, correspondingly, the side of the brain that controls it is awake. The unilateral hemispheric sleep of cetaceans, seals, and manatees allows them to swim while asleep and float to the surface to breathe so they don't drown. Dolphins, for example, seem to swim in the water without stopping, but in fact, they have a similar schedule to humans. But while sleeping, dolphins also swim all the time, and stay alert with one eye open and one eye closed. Scientists have discovered that the two hemispheres of the dolphin's brain sleep alternately. When one side is asleep, the other side is awake, and after a while, the two sides are exchanged, so that they take turns to be on duty and rest, and when they are strongly stimulated by the outside world, both hemispheres will be awake at the same time and respond quickly to the external situation.

Manatees sleep on the bottom of the sea.

This evolution has a different value for birds. During long-distance migrations, unilateral hemisphere sleep allows birds to fly in the right direction and stay alert while resting. It is interesting to note that when a flock of ducks settles down by the pond for the night, those lying on the edge of the periphery are more likely to open their outer eye and look out, of course, the corresponding cerebral hemisphere will be awake, while the duck sleeping in the middle of the flock can close both eyes with peace of mind. In this way, the ducks that keep vigil at the edge can protect the flock, at least not being "served by predators" in their sleep.

The duck sleeps with one eye open.

So will humans have a similar state?Masako Tamaki and colleagues at Brown University in the United States have proposed whether the first night effect is related to some type of sleep in both hemispheres of the brain, and whether it is a protective mechanism that can keep one hemisphere of the brain vigilant during sleep.

First, they conducted the first experiments to neuro-image the sleeping brain using techniques such as magnetoencephalography (MEG), structural magnetic resonance imaging (MRI), and polysomnography (PSG), during which they studied slow-wave activity (SWA) – the only sleep characteristic that reflects the depth of sleep – and which is also supported by cross-species local sleep studies, including mammals and birds. The experiment found that when the subjects spent the night in an unfamiliar environment for the first time, the slow-wave activity in the left hemisphere was lower than that in the right hemisphere, suggesting that the left hemisphere slept shallower than the right hemisphere during the first night, and the sleep depth of the left hemisphere returned to normal on the second night. Moreover, this asymmetrical sleep depth between the two hemispheres of the brain is found in the default pattern network, which is a network system that connects multiple brain regions and is active when people are distracted and distracted, allowing the brain to rest in a waking state. The degree of asymmetry is significantly related to the time to fall asleep, and therefore reflects the difficulty of falling asleep.

So, is this lighter sleep on the left side of the brain related to the detection of external signals?Masako Tamaki and colleagues did a second experiment, re-recruiting subjects and listening to a number of frequency-standard beeps while they were asleep, but mixed with some unusual sounds of different tones. The results showed that on the first day, when abnormal sounds appeared, the left hemisphere showed a greater response amplitude relative to the right hemisphere, while on the second day, the response amplitude of the left hemisphere decreased, while there was no significant difference in the response data of the right hemisphere on the two days. Thus, during the first night effect, the left side of the brain is more alert than the right side. And, through the abrupt and transient shift of electroencephalogram (EEG) frequency, they found that high alertness in the left hemisphere also led to more brain arousal during the first-night effect.

Does this wakefulness only manifest itself in the disruption of brain arousal and sleep?Is it possible to make people respond more quickly to abnormal stimuli from the outside?Masako Tamaki and his colleagues did a third experiment, using the same sound as in Experiment 2, replacing them with new subjects and asking them to tap their fingers when they heard a sound while sleeping. It was found that subjects woke up faster when sound came from the right ear (the right ear is connected to the left side of the brain), and the speed from hearing abnormal sounds to waking up was significantly faster on the first day than on the second day. These results suggest that the left hemisphere of the brain that is more alert during sleep can wake up the brain more quickly when an abnormal external stimulus is detected, so the first night effect can be said to be a survival protection mechanism in an unfamiliar environment.

The skill of "vigil" must be a very practical life-saving configuration in the era of ancestors, and it may gradually degenerate into the first night effect in the process of continuous evolution and inheritance, and it also brings people the trouble of recognizing the bed, so the next time you go out for the night, you may try to bring your own pillows and close-fitting clothes to create a feeling of being at home, and you may be able to fool your brain!

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