Can you recall a time you were sleeping and someone softly saying the sound of your voice roused you from a dream? This scene isn’t just archetypal, it actually says something about how our hearing works when we sleep. Sleep is described as an altered state that our body enters, and good sleep habits are beneficial for our overall health. While in general, sleep “powers down” our body’s sensory intake, there are indicators that our hearing may be more consistently “on” than “off”.
What Is Sleep and Why Do We Do It?
Although most of us hardly give it a thought, sleep is fascinating. During sleep our body recharges and regenerates itself. Studies have shown that our brain uses our time sleeping to prune down much of the sensory data it has received during the day, sloughing irrelevant occurrences and organizing important events. Sleep is also a time where the immune system of the body can work undisturbed by other demands – perhaps part of the reason our bodies demand more sleep when we are sick. The repair and rejuvenation state we enter into during sleep is called an “anabolic state”.
Sleep takes the body into a strange state, often compared to a suspended animation. While allowing our necessary bodily functions to continue, such as our lungs breathing and our heart beating, most other aspects of our biological systems go into a dulled and relaxed state. Sleep causes our muscles to relax and our nervous system to be less responsive to outside input. With our eyes closed, we cannot see while we are sleeping, and our senses of taste and smell are also dulled.
We fall into sleep in phases and cycle through different phases throughout time spent sleeping, with the deepest state of sleep marked by rapid eye movement beneath our eyelids, known as REM sleep. Other phases of sleep are all indicated by distinct brainwave patterns. Reaching an REM state during our sleep cycle is critical for healthy functioning of the body.
Hearing and Sleep
While closing our eyes acts as a sort of “off” button for our sense of sight, it is much harder to suspend our hearing. Our ears are always picking up sound, and new studies show that our hearing may be surprisingly alert even while we are fast asleep.
Of course, our nightly sleep state is calibrated delicately enough that our senses can still alert us when we perceive a threat. Feeling a sudden physical jolt, or hearing a loud crash will likely snap us out of our sleep state. While a truly hibernating animal will be so tuned out, even dramatic incoming threats may not rouse them, human sleep is much more alert.
Human hearing may be picking up and processing all the sounds in our surroundings, even when we aren’t aware of it. New French studies are confirming that the sleeping brain is quite responsive to recognizable phrases, voices and sounds – even prioritizing them over louder but less “relevant” noise. Researchers compared the brain response of sleeping subjects when incoherent speech-like noise was played versus clearly spoken and recognizable phrases, such as movie quotes. The brain patterns of sleepers seemed to easily prioritize the coherent significant speech over the garbled speech and responded with increased alertness and activity.
Let’s return to being gently stirred awake to the sound of our name. Speaking a recognizeable and highly significant word may be one of the simplest ways to get our brain’s attention- perhaps even more effective than a blaring alarm clock. It also indicates one of hearing’s super powers. Through learning, cognitive pattern forming and nuanced processing, our hearing is calibrated to respond to recognizable words and phrases.
This skill is what helps us pick out a specific conversation at a party or hear the voice of a friend in a crowd. It can also be one of the more difficult aspects of hearing loss. Hearing loss that is left untreated can leave us feeling left out of the social stream of our surroundings and less alert to what we are surrounded by. Fortunately, hearing loss doesn’t have to hold you back, it can be effectively treated with hearing aids. Hearing aids help you reconnect with healthy hearing so you can sleep easy.