your brain recognizes voices when you sleep

Sleep with television prevents you from get restful sleep. This is one of the conclusions that can be drawn from a recent study published on January 17 in the Journal of Neuroscience. Researchers from the University of Salzburg in Austria have revealed that the brain continues to respond selectively to environmental stimuli during sleep. Indeed, according to their work, the human brain reacts to unfamiliar voices while you are asleep in order to remain alert to potential threats. It acts as a sentry and thus remains in active “sleep” and analyzes unknown voices while you sleep. While monitoring the environment, he balances the need to protect your sleep and the possible need to wake up in the event of an external problem. “Our results highlight differences in brain responses to auditory stimuli based on their relevance to the sleeper,” the researchers state in their study.

No more sensory disturbances from unfamiliar voices

As reported by Daily Mail, which notably relays the study, to reach these conclusions, the researchers recruited 17 volunteers (14 women) with an average age of 22 years. The volunteers, all of whom had no reported sleep disturbances, were fitted with a polysomnography machine for a full night’s sleep. The Austrian researchers thus measured the brain activity of sleeping adults in response to familiar voices (like a parent) and unfamiliar voices (strangers). These voices pronounced via loudspeakers their first name as well as two unknown first names while a polysomnography recorded the activity of the brain. As a reminder, polysomnography measures brain waves, breathing, muscle tension, movement, heart activity and more as they progress through the different stages of sleep.

As a result, the researchers found that unfamiliar voices, such as those from a TV for example, elicited more K-complexes, a type of brain waves linked to sensory disturbances during sleep, compared to familiar voices. While familiar voices can also trigger K-complexes, only those triggered by unfamiliar voices were found to be accompanied by large-scale changes in brain activity related to sensory processing during participants’ sleep.

Sleeping with the TV prevents you from getting a good night’s sleep

“The results suggest that the unrecognized voice is a powerful promoter of brain responses during sleep non-rapid eye movement (NRE)”, the first phase of sleep. This study demonstrates that K-complexes allow the brain to enter a “sentinel mode of processing” during which the brain remains dormant but retains the ability to respond to outside stimuli. The researchers even found that brain responses to unfamiliar voices occurred less often as the night progressed, and unfamiliar voices gradually became more familiar, indicating that the brain may still be able to learn during sleep. “It may be that the sleeping brain learns, through repeated processing, that an initially unknown stimulus poses no immediate threat to the sleeper and therefore diminishes their response,” say the Australian researchers. Conversely, in a safe sleeping environment, “the brain can expect to hear familiar voices and systematically inhibits any response to such stimuli to preserve sleep”. The study therefore suggests that sleeping in a noisy environment with unfamiliar voices, such as those coming from a television, you prevent you from getting a night’s sleep restorative because the brain is in a higher level of alert. However, we know the devastating impact of lack of sleep.

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