Study: Acoustic Stimulation Improves Declarative Memory in Older Adults

A recent study found that pink noise—noise that has equal energy per octave and has lower-frequency components than white noise—is associated with improved declarative memory and slow wave activity (SWA) in healthy older adults.

Previous studies have shown that acoustic stimulation improves SWA and memory retention in young adults, but it is not known whether older adults, who typically have lower SWA than young adults, would experience similar benefits.
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In their study, the researchers assessed the influence of acoustic stimulation with pink noise on declarative memory and SWA in 13 cognitively healthy older adults aged between 60 and 84 years who were recruited from the Northwestern University Cognitive Neurology and Alzheimer’s Disease Center Clinical Core registry.

Participants completed 2 overnight visits at least 1 week apart, during which they listened to acoustic stimulation (STIM) for one visit and sham stimulation (SHAM) for the other visit. Participants were randomly assigned to STIM (n=6) or SHAM (n=7) on the first visit. In addition, participants completed a word-pair learning task and cued-recall test 90 minutes before sleeping and completed the delayed cued-recall test 1 hour after waking.

Through soft headphones, intervals of 5 pulses of pink noise (ON interval) were delivered during the upstate of the slow wave followed by a pause of approximately equal length (OFF interval).

The researchers found that SWA was similar during the entire sleep period between SHAM and STIM. However, SWA and spindle activity increased during STIM ON intervals compared with SHAM, and SWA was sustained across nearly the entire 5-pulse ON intervals compared with SHAM.

In addition, overnight word-pair recall increased by 26% and improved significantly after STIM compared with SHAM. Improvements in word recall correlated with changes in SWA between ON and OFF intervals.

“Using the phase-locked-loop method to precisely target acoustic stimulation to the upstate of sleep slow oscillations, we were able to enhance SWA and improve sleep-dependent memory storage in older adults, which strengthens the theoretical link between sleep and age-related memory integrity,” the researchers concluded.

They also agree that more research is needed to determine whether acoustic stimulation can safety and effectively be used as a non-invasive, long-term treatment for populations at risk for cognitive impairment.

—Melissa Weiss

Reference:

Papalambros NA, Santostasi G, Malkani RG, et al. Acoustic enhancement of sleep slow oscillations and concomitant memory improvement in older adults [published March 8, 2017]. Front Hum Neurosci. doi: doi.org/10.3389/fnhum.2017.00109.