Update 1: short-term memories are stored in the pre-frontal cortex, while the hippocampus stores long-term memories. The article has been updated with the correction.
A new finding on how the brain stores memories may help explain forgetfulness in elderly people, or in individuals suffering from poor sleep.
Neuroscientists at UC Berkley found slow brainwaves generated while we sleep play a key part in transporting memories from the prefrontal cortex to the hippocampus. The prefrontal cortex is our short-term memory bank, while the hippocampus stores long-term memories.
The problem is that as we grow older, memories may be getting jammed in the prefrontal cortex thanks to poor quality of sleep, and new memories rewrite the old ones.
“What we have discovered is a dysfunctional pathway that helps explain the relationship between brain deterioration, sleep disruption and memory loss as we get older – and with that, a potentially new treatment avenue,” said UC Berkeley sleep researcher Matthew Walker, an associate professor of psychology and neuroscience at UC Berkeley and senior author of the study published Jan. 27 in the journal Nature Neuroscience.
“When we are young, we have deep sleep that helps the brain store and retain new facts and information,” Walker said. “But as we get older, the quality of our sleep deteriorates and prevents those memories from being saved by the brain at night.”
For healthy adults, it’s estimated we spend a quarter of the night in deep, rapid-eye-movement (REM) sleep, when slow waves are generated by the brain’s middle frontal lobe. The study found that degenerated of the frontal lobe in elderly people was tied to their failure to enter the REM sleep state.
Improving Sleep for Better Memory
Researchers at UC Berkley will be conducting a study to see whether they can help improve the overnight memory of older adults.
“Can you jumpstart slow wave sleep and help people remember their lives and memories better? It’s an exciting possibility,” said Bryce Mander, a postdoctoral fellow in psychology at UC Berkeley and lead author of this latest study, in a press release.
So far, they’ve tested 18 younger adults (most in their 20s), and 15 elderly people (most in their 70s). They had each individual try to remember a 120-word set. According to the press release “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.”
They found the quality of sleep among the elderly participants was 75 percent lower than that of the younger participants, and the elderly participants did 55 percent worse on the memory tests.
According to the press release, however, “in younger adults, brain scans showed that deep sleep had efficiently helped to shift their memories from the short-term storage of the hippocampus to the long-term storage of the prefrontal cortex.”
Photo credit: By mark sebastian (Flickr: Laziest. Model. Ever. (#6228), via Wikimedia Commons.