These findings may help explain why it’s so difficult to sleep in new environments at first, since our brains take longer to sort out all the unfamiliar sounds and determine that we’re actually safe to stay in the new place.
To survive, our bodies must continue to function even while we sleep, and this is what our hard-working brains continue to do. And store our memories.
A new study was published in The Journal of Neuroscience. On January 17th, our brains will have a new task: to monitor our surroundings for alien danger in order to protect us.
Brain alarm for unfamiliar sounds
“Unfamiliar voices should not talk to you at night, they set off an alarm,” Manuel Chapus, a cognitive neuroscientist at the University of Salzburg, tells New Scientist.
Chabus and colleagues observed this brain alarm in 17 volunteers. After a night of adaptation to the new environment at the Salzburg Sleep Laboratory, volunteers underwent EEG recording, oxygen levels, heart rates, breathing and movement.
“We showed participants phonemes of their names and two unfamiliar names. These names were pronounced either in a familiar voice (FV) or an unfamiliar voice (UFV),” Mohamed Amin, the study’s first author and cognitive neuroscientist explained on Twitter.
As a Science Alert report notes, participants who were exposed to the faint, unfamiliar sounds showed a greater response than those who weren’t.
These responses included micro-arousals, short bouts of wake-like brain activity lasting only seconds. The function of ‘small excitability’ is not yet fully understood.
While both familiar and unfamiliar sounds elicited brainwave patterns called K-complexes, those who heard only the unfamiliar sounds experienced greater changes in brain activity associated with sensory processing. K-complexes are believed to prevent awakening in response to harmless disturbances.
“K-complexes may be the main mechanism shaping the way we sleep, helping the brain decide whether we should fall asleep or wake up,” Chabus tells Inside Science. “It’s a completely intelligent mechanism that allows you to know what is appropriate or not, and when it is appropriate, it will trigger a series of processes that facilitate the processing of that information without having to wake up and disrupt sleep.”
We learn while we sleep too
Taken together, these findings suggest that “the sleeping brain extracts sensory-relevant information for further processing,” according to Al-Amin. Previous research suggests that sensory processing of our environments persists even when we are unconscious, but what the new research adds is that the brain enters a “guardian mode” to perform this processing. “Our results present sounds that are unfamiliar or potentially more threatening, and therefore more exciting to the sleeper than familiar sounds,” the team wrote in their paper.
While the brain’s response to familiar sounds did not change after repeated exposure later in sleep, the response to unfamiliar sounds changed, becoming more impaired. This suggests that our brains not only process new information but learn from new information during sleep, perhaps deciding that unfamiliar and repetitive noises or sounds were not a threat, impairing future responses to them.
These findings may help explain why it is difficult to sleep in new environments at first, since our brains take longer to sort out all the unfamiliar sounds and determine that we are indeed safe to stay in the new place.
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