Search
06-2022

Our brains pay attention to unfamiliar sounds during sleep, study finds

A new study suggests that the human brain pays attention to unfamiliar sounds during sleep to alert them of potential dangers.

Researchers in Austria measured the brain activity of sleeping adults in response to familiar and unfamiliar voices.

Hearing unfamiliar sounds while sleeping causes the human brain to ‘tune in’ during non-rapid eye movement sleep (NREM), the first stage of sleep.

However, the researchers did not see the effect during REM, the deepest stage of sleep, possibly due to changes in microscopic structure in the brain, he says.

Even though our eyes are closed to the things around us, the brain continues to monitor the environment as we sleep, balancing the need to protect sleep with the need to stay awake.

According to experts, one way to accomplish this is by selectively responding to unfamiliar voices over familiar ones.

This can go back to a long process of human evolution, and the need to wake up early to face potential danger is characterized by less familiar auditory cues.

Overall, the study shows that unfamiliar sounds – such as sounds from TV – prevent a restful night’s sleep because the brain is on high alert.

During sleep the brain pays attention to unfamiliar sounds.  According to experts (stock image), this ability allows the brain to balance sleep in response to environmental cues.

During sleep the brain pays attention to unfamiliar sounds. According to experts (stock image), this ability allows the brain to balance sleep in response to environmental cues.

What is NREM sleep?

Non-rapid eye movement sleep (NREM) is the first stage of sleep.

Non-REM sleep occurs first and includes three phases.

The last two stages of non-REM sleep are when you fall into deep sleep. Waking up from this stage of sleep is difficult.

The study is led by researchers from the University of Salzburg and is published today in the journal Genurosie.

In their paper, the team said, ‘Our findings highlight discrepancies in brain responses to auditory stimuli depending on the sleeper’s relevance.

‘The results suggest that the unfamiliarity of voice is a strong promoter of brain responses during NREM sleep.’

For the study, researchers recruited 17 volunteers (14 female) with an average age of 22 years.

The volunteers, all of whom had no sleep disorders, were fitted with polysomnography equipment during a full night’s sleep.

Polysomnography measures brain waves, respiration, muscle tension, movement, heart activity, and more, as they move through the different stages of sleep.

Before the start of the experiment, participants were advised to maintain a regular sleep/wake cycle – approximately eight hours of sleep – for at least four days.

Prior to the experiments, volunteers were advised to maintain a regular sleep/wake cycle (approximately 8 hours of sleep) for at least four days.  They then spent two nights in the lab—the first time they were asleep with polysomnography (PSG) data, but they didn't hear any auditory stimuli.  PSG data was recorded for the second night while the auditory stimulus came from the loudspeaker during the night.  On both nights, participants were tested while awake, before and after falling asleep.

Prior to the experiments, volunteers were advised to maintain a regular sleep/wake cycle (approximately 8 hours of sleep) for at least four days. They then spent two nights in the lab—the first time they were asleep with polysomnography (PSG) data, but they didn’t hear any auditory stimuli. PSG data was recorded for the second night while the auditory stimulus came from the loudspeaker during the night. On both nights, participants were tested while awake, before and after falling asleep.

Finding your sleep ‘sweet spot’ may protect the brain

A 2021 study found that getting seven to eight hours of sleep each night is the best place to keep your brain healthy in old age.

People who regularly get less than six hours a day have poorer cognitive function and higher levels of a dangerous plaque in the brain linked to dementia.

Experts from Stanford University found that people who slept a lot also had poorer performance on tests of memory, reaction time and flexible thinking.

Read more: Finding your sleep ‘sweet spot’ will help protect your brain

As they fell asleep, they were presented with auditory stimuli via loudspeakers of their first name and two unfamiliar first names, either a familiar voice, (such as a parent) or an unfamiliar voice (a stranger). was spoken by.

Researchers found that unfamiliar voices produced more K-complexes, a type of brain wave associated with sensory disturbances during sleep, than familiar voices.

While familiar voices can also trigger the K-complex, only those triggered by unfamiliar voices were found with massive changes in brain activity associated with sensory processing, they found.

However, as the night passes, brain responses to unfamiliar sounds diminish and the voices become more familiar, indicating that the brain may still be capable of learning during sleep.

These results suggest that K-complexes allow the brain to enter a ‘sentinel processing mode’, where the brain remains asleep but retains the ability to respond to contextual stimuli.

‘It may be that the sleeping brain learns through repeated processing that the initially unfamiliar stimulus poses no immediate threat to the sleeper and consequently diminishes its response,’ the experts say.

‘Conversely, in a safe sleep environment, the brain may “expect” to hear familiar sounds and continuously inhibit any response to such stimuli in order to preserve sleep.’

The graph shows the difference between trigger K-complex and micro-stimulation.  The difference in the number of trigger K-complexes between the left, unfamiliar voice (UFV) and familiar voice (FV) was significant from 100ms to 800ms.  Well, the difference in the number of subtle stimuli between FVs and UFVs was significant over a period of 200 to 400ms, and 500 to 700ms

The graph shows the difference between trigger K-complex and micro-stimulation. The difference in the number of trigger K-complexes between the left, unfamiliar voice (UFV) and familiar voice (FV) was significant from 100ms to 800ms. Well, the difference in the number of subtle stimuli between FVs and UFVs was significant over a period of 200 to 400ms, and 500 to 700ms

As well as the K-complex, presenting auditory stimuli during NREM sleep increased the number of ‘spindles’ and ‘micro-stimulations’ in the brain.

‘Spindles are fast brain waves that appear during NREM sleep and are associated with memory consolidation,’ study author Amin Mohamed at the University of Salzburg told MailOnline.

‘Subtle arousal is a period of sleep during which the EEG signal changes from a slow and synchronized activity of sleep to a faster, wake-like activity.

‘By definition, they last from three seconds to 15 seconds; If they are long they are considered awakenings. They are visible in all stages of sleep.’

However, the researchers found no difference in the amount of K-complex, spindle, or subtle stimuli triggered between the subject’s own name and unfamiliar names.

This is interesting because previous research – including a 1999 study by a French team – has demonstrated that the subject’s own name evokes stronger brain responses than other names during sleep.

four stages of sleep

Pictures, different stages of the nocturnal sleep cycle.  Most dreams occur during REM sleep (marked in red) although some may also occur in non-REM sleep.

Pictures, different stages of the nocturnal sleep cycle. Most dreams occur during REM sleep (marked in red) although some may also occur in non-REM sleep.

Sleep is generally separated into four phases. The first three of these are known as ‘non rapid eye movement’ or NREM sleep.

The final stage is known as rapid eye movement or REM sleep.

A normal night’s sleep goes back and forth between phases.

first stage: The first five minutes or so after we leave we are not sleeping soundly.

We are still aware of our surroundings but our muscles begin to relax, the heartbeat slows down and brainwave patterns, known as theta waves, become irregular but rapid.

Although we are asleep during Stage 1, we can wake up with the feeling that we have not slept at all.

After about five minutes our bodies move into the second phase.

Phase 2: This is when we have gone to sleep, and if we wake up you will know that we are sleeping. It’s still easy enough to wake up.

This phase is characterized by short bursts of electrical activity in the brain known as spindles and large waves known as the K-complex, which indicate that the brain is still in place before shutting down on a subconscious level. Knows about what is happening around it. ,

The heartbeat and breathing slow, and the muscles relax even more.

Our body temperature drops and the movement of the eyes stops.

Brain wave activity slows down but is marked by brief bursts of electrical activity.

step 3Stage 3 non-REM sleep is the period of deep sleep we need to feel refreshed in the morning.

This happens over a long period of time during the first half of the night.

During sleep our heartbeat and breathing slow down to their lowest level and brain waves slow down even more.

Our muscles are relaxed and it can be difficult for people to wake us up.

The body repairs muscles and tissues, stimulates growth and development, enhances immune function and builds energy for the next day.

Hypnagogia — the transitional state between wakefulness and sleep — is associated with NREM stages one through three.

Psychic events during hypnosis include lucid thoughts, lucid dreaming, hallucinations, and sleep paralysis.

ram sleepREM sleep first occurs approximately 90 minutes after sleep.

Our eyes move rapidly from side to side behind closed eyelids.

Mixed frequency brain wave activity becomes close to the activity seen in wakefulness.

Our breathing becomes rapid and irregular, and heart rate and blood pressure rise almost to the level of wakefulness.

Most dreams occur during REM sleep, although some may also occur in non-REM sleep.

The muscles of the arms and legs become temporarily paralyzed, which prevents us from fulfilling our dreams.

As we age, we spend less time in REM sleep.

Memory consolidation most likely requires both non-REM and REM sleep.

Source: US National Institutes of Health

,

Nation World News is the fastest emerging news website covering all the latest news, world’s top stories, science news entertainment sports cricket’s latest discoveries, new technology gadgets, politics news, and more.

LATEST NEWS

Related Stories