Using Sound to Boost Sleep

There have been intriguing findings on the effects of sounds presented during sleep on the quality of sleep, as well as the function of sleep in memory and learning.

One of the most intriguing questions for scientists is why we sleep. Humans spend on average a third of their lives asleep. This means that during a lifetime of 80 years, you will have slept for 26.6 years, or 9709 days, or 233,016 hours. The staggering amount of time spent sleeping has led researchers to believe that something important must be going on during those night hours.
 
According to research, sleep has many important functions. For one, it plays an important part in physical recovery, as during sleep the body focuses on building muscles and nerves. Sleep is also highly important for healthy cognitive function. For instance, even just one night of inadequate sleep will decrease ability for creativity and flexibility of thought, making one more prone to repetitive, monotonous thought. It has also been found that sleep is required for learning, because during sleep memory of new information forms and stabilizes- what scientists call “consolidation”.

There is already ample evidence that music is an effective and enjoyable way to manage sleep disturbances such as insomnia. In recent years, there have been intriguing findings on the effects of mere sounds presented during sleep on the quality of sleep, as well as the function of sleep in memory and learning. 

Slow wave” strength with sounds during deep sleep has been shown to make a real difference in cognitive functioning

During sleep, the brain alternates between different states. One state is REM (rapid eye-movement) sleep during which people often see vivid dreams. REM sleep is characterized by electrical brain activity that seems similar to the activity during wakefulness, with irregular, high frequency peaks that can be seen with an electroencephalogram. In addition to REM, there are phases of deep sleep, sometimes called slow-wave sleep because of the slow, steady, rhythmic waves that can be seen in the brain’s electrical activity. The different phases of sleep seem to have different roles in memory formation and learning. For instance, slow-wave sleep is needed for long-term memory formation. This is something that students engaged in all-night study sessions for their examinations should consider – you need to give your brain time to sleep to create memories of the new information!
 
Because of the importance of slow-wave sleep, scientists have thought that perhaps boosting this sleep phase could actually lead to better learning results. How could this be done?
 
This is where sound comes in: there is research showing that the brain’s oscillatory activity can actually be stimulated by sound. Why? Well, brain oscillations, or steady waves of activity, always occur at a certain frequency. During slow-wave sleep, the brain shows oscillations occurring around 1 Hz, meaning one wave per second. Researchers have found that presenting a sleeping individual with sounds that are in sync with the brain waves strengthens the power of the oscillations. Remarkably, this enhancement of slow wave strength with sounds during deep sleep has been shown to make a real difference in cognitive functioning. Individuals who were exposed to short bursts of pink noise in sync with their brain’s oscillations during phases of deep sleep showed better memory of the material they had learned just before turning in!
 
In summary, exciting new lines of research are opening up regarding the enhancement of different phases of sleep, and thereby supporting functions like memory and learning with something as simple as repeating sounds. Investigations are already underway examining whether not only pink noise but also musical tones could be used to gain similar enhancement of sleep phases important for learning. Perhaps in the future we could have individually designed soundtracks for nighttime that not only deepen our sleep, but also enhance all the functions that sleep is important for.

written by ketki karanam

 

references:

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Harrison, Y., & Horne, J. A. (1999). One Night of Sleep Loss Impairs Innovative Thinking and Flexible Decision Making. Organizational Behavior and Human Decision Processes, 78(2), 128–145. doi:10.1006/obhd.1999.2827

Ngo, H.-V. V., Claussen, J. C., Born, J., & Mölle, M. (2012). Induction of slow oscillations by rhythmic acoustic stimulation. Journal of Sleep Research, 22(1), 22–31. doi:10.1111/j.1365-2869.2012.01039.x

Ngo, H.-V. V., Martinetz, T., Born, J., & Mölle, M. (2013). Auditory Closed-Loop Stimulation of the Sleep Slow Oscillation Enhances Memory. Neuron, 78(3), 545–553. doi:10.1016/j.neuron.2013.03.006

Stickgold, R., James, L., & Hobson, J. A. (2000). Nature Neuroscience, 3(12), 1237–1238. doi:10.1038/81756

Stickgold, R. (2005). Sleep-dependent memory consolidation. Nature, 437(7063), 1272–1278. doi:10.1038/nature04286