Senior author sleep researcher Matthew Walker of the University of California, Berkeley, said the slow brain waves generated during the deep restorative sleep play a key role in transporting memories from the part of the brain which provides short-term storage for memories to the part of the brain that stores long-term memories.
However, 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, Walker and colleagues found.
"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," Walker said.
"When we are young, we have deep sleep that helps the brain store and retain new facts and information, but as we get older, the quality of our sleep deteriorates and prevents those memories from being saved by the brain at night."
The study was published the journal Nature Neuroscience.