Gentle sound stimulation — such as the rush of a waterfall — synchronized to the rhythm of brain waves can significantly improve deep sleep and memory in older adults, according to a new study published in the journal Frontiers in Human Neuroscience.
Deep sleep is essential for memory consolidation. Beginning in middle age, however, deep sleep becomes harder to obtain for many people — a problem which scientists believe contributes to memory loss in aging.
Prior research has shown that acoustic simulation played during deep sleep can help improve memory consolidation in young people. But so far, this approach had not been tested in older adults. So for the new study, the researchers focused on older individuals, who have much more to gain memory-wise from enhanced deep sleep.
During deep sleep, each brain wave or oscillation slows to about one per second compared to 10 oscillations per second during wakefulness. Giovanni Santostasi, a study coauthor, developed an algorithm that delivered the sound during the rising portion of slow wave oscillations. This approach was able to read an individual’s brainwaves in real time and lock in the gentle sound stimulation during a precise moment of neuron communication during deep sleep — a moment that varies for each person.
After the sound stimulation, the older participants’ slow waves increased during sleep. The findings reveal that this process significantly enhanced deep sleep in participants and boosted their scores on a memory test.
“This is an innovative, simple, and safe non-medication approach that may help improve brain health,” said senior author Dr. Phyllis Zee, professor of neurology at Northwestern University Feinberg School of Medicine and a Northwestern Medicine sleep specialist. “This is a potential tool for enhancing memory in older populations and attenuating normal age-related memory decline.”
For the study, 13 participants (aged 60 and older) were recruited from the Cognitive Neurology and Alzheimer’s Disease Center at Northwestern. Each participant received one night of acoustic stimulation and one night of sham stimulation. The sham stimulation session was identical to the acoustic one, but the noise was turned off during sleep. For both the sham and acoustic stimulation sessions, the individuals took a memory test at night and again the next morning.
The morning after the sham stimulation, recall ability improved by a few percentage points. However, after the noise stimulation, the average improvement was three times greater. The degree of slow wave sleep enhancement was tied to the degree of memory improvement, suggesting slow wave sleep remains essential for memory, even in old age.
While the researchers have not yet studied the effect of repeated nights of stimulation, this sound approach could be a viable intervention for longer-term use in the home, Zee said.
Larger studies are needed to confirm the efficacy of this method and then “the idea is to be able to offer this for people to use at home,” said first author Nelly Papalambros, a Ph.D. student in neuroscience working in Zee’s lab. “We want to move this to long-term, at-home studies.”
Source: Northwestern University