Researchers at UC Berkeley found deep ‘slow wave’ sleep could restore memory as we age.
Improving sleep quality could provide a memory boost in older people who may have difficulty remembering things like people’s names, according to neuroscientists at the University of California, Berkeley.
For their study, the researchers tested memory in 18 healthy adults mostly in their twenties, and 15 healthy adults in their seventies after a full night’s sleep. Before going to sleep, participants learned and were tested on 120 sets of words.
As they slept, an electroencephalographic (EEG) machine measured their brain wave activity. The next morning, they were tested again on the word pairs, but this time while undergoing functional and structural magnetic resonance imaging (fMRI) scans.
The researchers discovered that in older adults, getting inadequate amounts of “slow-wave” sleep may cause memories to get stuck in the short-term memory storage area in the hippocampus — rather than moving to a long-term storage area in the prefrontal cortex — and then the memories get lost or are overwritten by new memories.
Slow-wave sleep is often referred to as deep sleep and consists of stage 3 and 4 of non-rapid eye movement sleep.
The slow brain waves created during deep sleep when people are young play a key role in transporting memories from the hippocampus to the prefrontal cortex. Slow waves are formed by the brain’s middle frontal lobe. Deterioration of this part of the brain in elderly people is linked to the poor quality of sleep people get as they age.
“When we are young, we have deep sleep that helps the brain store and retain new facts and information,” explained Matthew Walker, PhD, associate professor of psychology and neuroscience at UC Berkeley and senior author of the study, in a press release. “But as we get older, the quality of our sleep deteriorates and prevents those memories from being saved by the brain at night.”
For the older adults in the study, there was a clear link between the degree of brain deterioration in the middle frontal lobe and the severity of diminished slow-wave activity during sleep. The quality of their deep sleep, on average, was 75 percent lower than that of the younger participants, and their memory of the word pairs the next day was 55 percent worse than the day before.
For those in the younger age group, the brain scans showed deep sleep had helped shift their memories from the hippocampus to the prefrontal cortex with the help of slow brain waves, according to the press release, and the discovery that slow waves in the frontal brain help strengthen memories could pave the way for treatments for memory loss in the elderly, like direct current stimulation or new drugs.
By Erin Hicks