Our brain pays attention to Unfamiliar Voices during sleep to stay alert to potential threats. Researchers in Austria measured the brain activity of sleeping adults in response to familiar and Unfamiliar Voices.Hearing Unfamiliar Voices when asleep caused the human brain to ‘tune in’ during non-rapid eye movement sleep (NREM), the first stage of sleep. Researchers didn’t see the effect during REM, the deepest stage of sleep, likely due to microstructure changes in the brain, they say.
Our eyes are shut off from what’s around us; the brain continues to monitor the environment as we sleep, balancing the need to protect sleep with the need to wake up. It accomplishes this by selectively responding to Unfamiliar Voices over familiar ones.This may go back to the long process of human evolution and the need to quickly awake in the face of potential danger, characterized by less familiar auditory cues. The study suggests Unfamiliar Voices – like those coming from a TV – prevent a restful night’s sleep because the brain is on higher alert.
The study has been led by researchers at the University of Salzburg and published today in the journal JNeurosci. ‘Our findings highlight discrepancies in brain responses to auditory stimuli based on their relevance to the sleeper,’ the team says in their paper. The study results suggest that the unfamiliarity of voice is a strong promoter of brain responses during NREM sleep.
For the study, researchers recruited 17 volunteers with an average age of 22 years. The volunteers, all of whom had no reported sleep disorders, were fitted with polysomnography equipment during a whole night’s sleep. Polysomnography measures brain waves, respiration, muscle tension, movements, heart activity and more, as they advance through the different sleep stages.