Sound Stimulation

Even if grade school was years or decades ago, it’s easy to recall the horror of French vocabulary quizzes and having to memorize all 33 lines of Hamlet’s “To Be or Not to Be” soliloquy. And while the trials of memorization are easy to remember, ironically, recalling of lists of vocabulary and facts is somewhat more difficult.

Wouldn’t it be nice if, when you were asleep, facts you learned the night before were gently reinforced in your mind? What if all you had to do was…listen? In a small study, researchers at the University of Tübingen in Germany have observed that by synching closed-loop “pink noise,” a controlled noise track calibrated to match the brain’s activity during slow-wave sleep, your sleep and memory can be improved.

Amber Waves of Brain

Eleven student volunteers were tested on two different nights, during which pink noise tracks were used in synch with the slow oscillations (SO) of their brain waves. Your brain activity oscillates at different frequencies depending on what you’re doing, how high your stress level is, and other factors, such as the amount of sleep, nourishment, and stimulation you receive. SO are critically important for processing information and consolidating memories during sleep.

While folk wisdom in high school and college says that studying before sleep helps you retain information, these German researchers took the myth to the mat. They used sound stimulation to “enhance the slow oscillation rhythm of slow wave sleep,” said Jan Born, study co-author and director of the Department of Medical Psychology and Behavioral Neurobiology at the University of Tübingen.

Using an electroencephalograph, or EEG, which charts the brain's electrical activity through the scalp, the researchers detected SO. Once detected, sounds were delivered to the ears in synch with the upswing of SO. Because your brain activity swings between up- and down-states, researchers guessed that synching the sound frequency with these different states would improve memory.

“The big surprise for us was how effective this type of stimulation was, both in terms of enhancing the brain’s slow oscillation rhythm and in improving the consolidation of memories the student volunteers had learnt before the sleep interval in the lab,” Born said.

After receiving sound stimulation, participants were much better able to recall vocabulary pairs they had learned the night before than when they didn’t listen to the pink noise track.

Not MP3 Ready…Yet

For those looking for a quick pre-test boost, sound stimulation is still, unfortunately, in the exploratory stages. But the benefits of closed-loop auditory stimulation appear promising.

“It might [also] be used to deepen sleep in certain forms of insomnia,” Born said. Because it is a non-invasive technique, it could be ideal for improving sleep and memory in insomniacs and perhaps even improving attention in children with ADHD.

Before pink noise is applied practically, researchers must test the limits of the technique. “Can SO be further enhanced by even more persistent ‘in phase’ auditory stimulation, or is there a kind of natural brake in the brain that prevents an ‘overdrive?’” Born wonders.

For now, flash cards and all-nighters may have to do.

Learn More: