What You May Be Hearing When You Sleep

Have you ever wondered about what you hear at night? If so, you’re not alone. The topic of whether or not our hearing stays on even when our other senses have turned off during sleep has been one of considerable debate.

New research may now be showing that we do, in fact, process auditory information in our sleep. These findings could prove valuable in the future for those who use hearing technology for hearing loss.

Naptime hearing

Research from Vanderbilt University recently released preliminary results from an EEG study that offered surprising insight into hearing and sleep. In the study, the team worked with a group of preschool-age children at the university’s preschool. The children were placed in a quiet and isolated room for naptime, and while they were asleep, researchers played a group of three nonsense words over a short period. The preschoolers’ brainwaves were tested using an EEG machine.

Following the nap, the team showed the kids a variety of nonsense words, including those played during naptime.

According to the results, the children showed signs of recognition for the naptime nonsense words, confirming the hypothesis that they were still hearing and processing sounds while asleep.

Researchers dig into hearing during sleep

This isn’t the first study to take a closer look at whether or not we process auditory information during sleep, how it happens and how it affects us. It has been a question that has intrigued scientists for years:

• In a 2016 study, a team from the École Normale Supérieure in Paris used EEG to monitor the brains of volunteers listening to recordings of spoken words. Participants were asked to classify these words as either objects or animals. The results showed varying degrees of information processing depending on the depth of sleep (light non-REM, non-REM or REM).
• Earlier findings from Johns Hopkins also took a look at how the brain processes sound during sleep and why some sounds seem to wake us while others don’t. In this study, an undergraduate student uncovered where in the frontal cortex this process might take place. “We found that during waking, only areas around primary auditory cortex are activated by the tones,” Serena J. Gondek, study lead and author said. “Then, during light and deep sleep, you find not only primary auditory activation, but the frontal lobe also responds.”
• Another study published in Current Biology in 2014 found that sleeping participants were able make decisions (“task relevant responses”) in response to spoken words. The study reiterated previous findings that the brain does not completely shut down and disconnect during sleep as we once thought.

As researchers continue to explore how and what we hear while sleeping, experts believe this valuable information not only helps us to understand better how hearing works but may also one day translate into better hearing technology and treatment options for those with hearing loss.

If you have questions about your hearing or believe you have hearing loss, contact our office to schedule an appointment for a hearing evaluation.