Sleeping In Strange Houses: A Dangerous Mistake

Have you ever noticed that you sleep better in your own bed than in a hotel or a friend's house? This phenomenon is called the first night effect, and scientists have discovered that it occurs because one half of the brain remains alert and on night watch while the other half falls asleep. This is similar to how birds and dolphins sleep with one eye open to watch out for predators. The left hemisphere of the brain, which remains awake, is also more responsive to high-pitched sounds, which could indicate a threat. This effect disappears on the second night, as the brain gets used to the new environment.

The first night effect is a phenomenon where people experience poor sleep in a new place

Scientists have studied sleeping brains for half a century to understand this phenomenon. In a study published in 2016, a team from Brown University used brain imaging techniques to monitor how 35 people slept in a laboratory setting. The scans revealed that the right halves of the participants' brains fell asleep as normal, but the left hemispheres remained more active, indicating wakefulness. This suggests that when in an unfamiliar place, one side of the brain stays alert to monitor for potential threats in the environment.

The study also found that the left side of the brain showed a larger response to high-pitched sounds compared to the right, indicating increased vigilance in that hemisphere. Interestingly, these asymmetries were only observed on the first night of sleep in a new place, and the effect disappeared on the second night.

The first night effect is a real phenomenon that has been known about for a long time, and it can be a model of sleep disruption. People who frequently sleep in new places may experience less of this effect as their brains get used to the variation. To reduce the impact of the first night effect, some suggestions include taking your own pillow when travelling or staying in places with similar rooms.

One half of the brain remains awake as a night watch system in unfamiliar surroundings

When we sleep in a new place, one half of our brain remains alert while the other half enjoys deeper sleep. This phenomenon is known as the "first-night effect" in the field of human sleep research.

In a study conducted by Masako Tamaki, a sleep scientist at Brown University, 35 participants' brain activities were recorded for 90 minutes as they slept. The scans revealed that while the right halves of the participants' brains fell asleep normally, the left hemispheres remained more active. This suggests that one side of the brain acts as a "night watch system" to monitor unfamiliar surroundings during sleep.

The left hemisphere's vigilance was further confirmed by testing how people responded to sounds while asleep. The brains largely ignored the low-pitched tones played every second but jolted into action when an unusual sound, such as a high-pitched tone, was added. The left side of the brain responded more to these deviant tones, and people were more likely to wake up. This indicates that the brain's night watch system is alert to unusual sounds that could represent a threat.

This night watch system might be an evolutionary advantage, ensuring our safety in unfamiliar surroundings. It is similar to the survival strategy employed by birds and marine mammals, who are known to sleep with one eye open or alternate sleep between brain hemispheres to watch for predators.

While the specific hemisphere that stays alert may vary, the "first-night effect" highlights the fascinating way our brains adapt to new environments, ensuring we remain vigilant even during sleep in unfamiliar surroundings.

This may be the human equivalent of birds and dolphins sleeping with one eye open

Dolphins and some bird species have developed a unique way of sleeping—keeping one eye open and one half of their brain awake while the other half sleeps. This is known as unihemispheric slow-wave sleep (USWS). In the case of dolphins, this adaptation allows them to continue swimming and surfacing for air while they sleep. It also helps them to monitor for predators and maintain their body temperature.

Humans don't typically engage in classic USWS, but a similar phenomenon has been observed. When sleeping in a new place, one half of the human brain may remain on night watch while the other half sleeps. This is known as the "first night effect" and is thought to be a safeguard mechanism to protect us from potential threats in unfamiliar surroundings. Like dolphins and birds, we may be able to detect unusual sounds that could represent a danger.

This ability to sleep with "one eye open" is a brilliant evolutionary adaptation that allows species to balance the need for rest with the need to protect themselves from predators. While it can be unnerving to experience the first night effect as a human, it's reassuring to know that our brains are looking out for us, even when we're asleep.

Further research into USWS in animals may even help us understand and treat human sleep disorders, which often affect one brain hemisphere more than the other. So, the next time you find yourself struggling to sleep in a strange house, remember that your brain is keeping you safe—just like a bird or a dolphin.

The left hemisphere of the brain shows wakefulness while the right shows sleep

Sleep is essential for our brains to function properly. While we sleep, our brains remain remarkably active, and sleep affects almost every type of tissue and system in the body.

When we sleep in a new place, our brains spend the first night in "surveillance mode". One hemisphere goes to sleep while the other half of the brain remains on "night watch". This phenomenon is known as the "first-night effect".

Research has shown that the left hemisphere of the brain is more vigilant and responsive to unusual sounds during the first night in a new place. This is thought to be an evolutionary adaptation, allowing us to monitor unfamiliar environments for potential threats while we sleep.

The "first-night effect" is comparable to the unihemispheric sleep found in birds and aquatic mammals such as dolphins and whales. These animals keep one eye open and one half of their brain awake to stay alert for predators while they sleep.

While the left hemisphere of the brain shows wakefulness during the first night in a new place, it is not known if this pattern continues throughout the night. It is possible that the brain switches its night watch system from one side to the other during sleep.

Understanding the "first-night effect" can help explain why people often experience disturbed sleep when staying somewhere new. It also highlights the complex and dynamic nature of sleep, which scientists are still working to fully understand.

The effect disappears on the second night

Scientists have studied sleeping brains for half a century to understand why this happens. In a recent study, researchers from Brown University used brain imaging techniques to monitor how 35 people slept in a laboratory. The scans revealed that on the first night, the right halves of the participants' brains fell asleep, but the left hemispheres remained more active, staying alert for any unusual sounds that could represent a threat. However, this effect vanished on the second night.

So, if you're struggling to sleep in a strange house, take comfort in knowing that it's likely just your brain's natural surveillance mode kicking in. The good news is that you should sleep better on the second night!

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