The connection between poor sleep, memory loss and brain deterioration as we grow older has been elusive, but a new discovery could help fill the gaps between sleep and memory. The findings, appearing in Nature Neuroscience, shed new light on some of the forgetfulness common to the elderly that includes difficulty remembering people's names.
University of California - Berkeley neuroscientists have found that the slow brain waves generated during the deep, restorative sleep we typically experience in youth play a key role in transporting memories from the hippocampus - which provides short-term storage for memories - to the prefrontal cortex, which stores longer term memories.
UC Berkeley sleep researcher Matthew Walker thinks that in older adults, memories may be getting "stuck" in the hippocampus due to the poor quality of deep "slow wave" sleep, and are then overwritten by new memories.
"When we are young, we have deep sleep that helps the brain store and retain new facts and information," Walker explained. "But as we get older, the quality of our sleep deteriorates and prevents those memories from being saved by the brain at night."
Healthy adults typically spend one-quarter of the night in deep, non-rapid-eye-movement (REM) sleep. Slow waves are generated by the brain's middle frontal lobe. According to Walker, deterioration of this frontal region of the brain in elderly people is linked to their failure to generate deep sleep.
In older adults, brain scans showed a clear link between the degree of brain deterioration in the middle frontal lobe and the severity of impaired "slow wave activity" during sleep. On average, the quality of deep sleep in the elderly was 75 percent lower than that of the younger participants, and their memory was 55 percent worse.
The discovery that slow waves in the frontal brain help strengthen memories may pave the way for therapeutic treatments for memory loss in the elderly, such as transcranial direct current stimulation or novel drugs. "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," said Walker.
"Can you jumpstart slow wave sleep and help people remember their lives and memories better? It's an exciting possibility," added co-researcher Bryce Mander.
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Source: University of California - Berkeley