Pink noise is defined as gentle, soothing sound whereby each octave possesses equal energy. In essence, pink noise is the background noise that we hear in everyday environments.
Researchers from Northwestern University in Evanston, IL, found that when they synced pink noise to the brain waves of older adults as they slept, the sound not only enhanced their quality of deep sleep, but it also improved their memory.
Senior author Dr. Phyllis Zee, professor of neurology at the Feinberg School of Medicine at Northwestern, and colleagues recently published their findings in the journal Frontiers in Human Neuroscience.
Numerous studies have highlighted the importance of sleep for memory consolidation – that is, the brain’s ability to convert short-term memories into long-term memories.
Slow-wave sleep (SWS) – more commonly referred to as deep sleep – is part of the non-rapid eye movement (NREM) sleep cycle that is considered important for memory consolidation. As we get older, however, the quality of SWS can decrease.
Studies have shown that disruptions to NREM sleep in older age can have negative consequences for memory.
According to Dr. Zee and team, previous research in young adults has uncovered a link between acoustic stimulation of slow-wave brain activity during sleep and improved memory. However, they note that studies using acoustic stimulation in older adults are lacking.
Acoustic stimulation boosts SWS, memory in later life
To address this gap in research, Dr. Zee and colleagues enrolled 13 older adults, aged between 60 and 84 years, to their study.
All adults were subject to one night of sham stimulation and one night of acoustic stimulation, which were around 1 week apart. The acoustic stimulation incorporated pink noise that was synced to their brain waves as they slept.
For each session, the adults completed two memory recall tests – one before they went to sleep at night, and one after they woke up the following morning.
While memory recall improved under both conditions, the researchers found that the average improvement following acoustic stimulation was three times greater than with the sham stimulation.
The greater improvement in memory as a result of acoustic stimulation correlated with a greater increase in the quality of SWS, which the team says emphasizes how important deep sleep is for memory consolidation, even in later life.
Overall, the researchers believe that their findings indicate that acoustic stimulation may be an effective way to boost sleep quality and memory in older age.
“This is an innovative, simple, and safe non-medication approach that may help improve brain health. This is a potential tool for enhancing memory in older populations and attenuating normal age-related memory decline.”
Dr. Phyllis Zee
However, the team concludes that further studies involving a larger number of participants are needed before acoustic stimulation can be recommended for older adults.
“We want to move this to long-term, at-home studies,” notes first author Nelly Papalambros, of the Department of Neurology at the Feinberg School of Medicine.