For decades scientists have known that the ability to remember newly learned information declines with age, but it was not clear why. A new study may provide part of the answer.
The report, posted online on Sunday by the journal Nature Neuroscience, suggests that structural brain changes occurring naturally over time interfere with sleep quality, which in turn blunts the ability to store memories for the long term.
Previous research had found that the prefrontal cortex, the brain region behind the forehead, tends to lose volume with age, and that part of this region helps sustain quality sleep, which is critical to consolidating new memories. But the new experiment, led by scientists at the University of California, Berkeley, is the first to link structural changes directly with sleep-related memory problems.
The findings suggest that one way to slow memory decline in aging adults is to improve sleep, specifically the so-called slow-wave phase, which constitutes about a quarter of a normal night’s slumber.
Doctors cannot reverse structural changes that occur with age any more than they can turn back time. But at least two groups are experimenting with electrical stimulation as a way to improve deep sleep in older people. By placing electrodes on the scalp, scientists can run a low current across the prefrontal area, essentially mimicking the shape of clean, high-quality slow waves.
The result: improved memory, at least in some studies. “There are also a number of other ways you can improve sleep, including exercise,” said Ken Paller, a professor of psychology and director of the cognitive neuroscience program at Northwestern, who was not involved in the research.
Dr. Paller said that a whole array of changes occurred across the brain during aging and that sleep was only one factor affecting memory function.