Memory lapses are more common and frequent in the elderly, perhaps because their brain waves can’t sync to save new memories, researchers at University of California, Berkeley found.
In stage 4 sleep, the brain produces delta waves almost exclusively. It is very difficult to wake someone during stages 3 and 4, which together are called deep sleep. There is no eye movement or muscle activity.
During deep sleep (Non-REM, Stage-4 sleep), seniors have less coordination between brain waves. Short-term memories will convert into long-term memories when slow waves during NREM sleep and speedy electrical bursts called spindles contact at just the right moment. This contact takes approximately one-tenth of a second. Researchers found that these brain rhythms move in perfect lockstep in young adults, but this synchronization declines with age.
They suspect the aging brain can’t coordinate the two deep-sleep brain waves, most likely because of atrophy in a brain region involved in restorative sleep. The worse the atrophy, the more the deep-sleep brainwaves are out of step.
This mistiming prevents seniors from being able to save new memories, leading to overnight forgetting rather than remembering, the researchers report. As the brain ages, it cannot precisely coordinate these two deep-sleep brain waves.
Memory: The Study Protocol
For the study, researchers compared the overnight memory of 20 healthy adults in their 20s to that of 32 healthy older adults, aged 70 and older. Participants learned 120 word sets before going to bed for the night. Researchers used electrodes to record their electrical brain-wave activity while they slept. The next morning, participants were tested on the word pairs while having their brain scanned.
They found the timing was consistently off and waves couldn’t sync for seniors, which may explain how aging can affect memory for healthy older adults and certainly can be much worse for those with dementia.
The study suggests that sleep may be the answer to its own problem. A possible solution, apply electrical brain stimulation, so that the brain can re-synchronize and boost memory retention.