Israeli researchers discover tiny brain region controlling sleep depth

JERUSALEM, July 6 (Xinhua) -- Israeli researchers have found that a tiny region in the brainstem is a key factor that determines how deeply everyone sleeps, Tel Aviv University (TAU) in central Israel said on Monday.

This region, called the locus coeruleus, secretes the chemical noradrenaline throughout the brain.

These findings may lead to the development of novel methods to improve sleep quality.

In a study, published in the journal Science Advances, a team of TAU researchers explored the reasons why, during sleep, people rarely respond to external stimuli such as sounds even though the brain remains highly active.

The study found that noradrenaline, which is secreted in response to stress, lies at the heart of the human ability to "shut off" sensory responses and sleep soundly.

During good, deep sleep, which is critical for health, people rarely respond to external stimuli such as sounds, unless they are strong enough, like an alarm clock, or meaningful, like a baby's cry.

However, the higher the activity is in this brain system, the more likely to wake up from a sound.

The team found in rat experiments that the normal healthy situation is for noradrenaline activity to be silent or minimal during sleep, but when it is high, waking up will be more frequent, even from low-volume sounds.

This discovery can explain the changes in sleep quality differences, as light sleepers wake up from every faint sound, while deep sleepers can sleep through just about anything.

"Our findings clearly show that the locus coeruleus noradrenaline system is a powerful 'dial' that controls the depth of sleep despite external stimuli," the researchers concluded.

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