Both memory loss and disrupted sleep are hallmarks of old age. But could it be that one is directly tied to the other? Neuroscientists from the University of California, Berkeley think so. Approximately one quarter of a good night’s sleep is devoted to deep, non-rapid-eve-movement (REM) sleep. It is during this time that the brain restores itself, sifting through memories and moving them from short-term storage into the prefrontal cortex for long-term retention. However, this part of the brain is often deteriorated in elderly people.
A recent UC Berkeley study used electroencephalographic (EEG) machines and fMRI scans to show a link between brain deterioration in the middle frontal lobe and the severity of impaired slow wave activity during sleep. This leads researchers to believe that memories are getting jammed up in short-term storage, never making their way to the prefrontal cortex. In simpler terms, an atrophied prefrontal cortex may very well be the culprit behind disrupted sleep in the elderly. This, according to the study, has a detrimental effect on long-term memory. Study participants reinforced this theory when they underwent a rigorous memory test. Participants (made up of 18 healthy young adults and 15 healthy older adults) learned 120 different word sets and were tested on them before going to bed. After a full night’s sleep, they were tested again. On average, the quality of deep sleep in the older adults was 75 percent lower than that of their younger counterparts. Additionally, their recall of the word pairs from the day before was 55 percent worse. “It was surprising how strongly disrupted deep sleep was associated with impaired memory in older adults, predicting memory deficits more accurately than age or brain atrophy,” said Bryce Mander, the study’s lead author. These findings open the door to new treatment possibilities, including transcranial direct current stimulation to help strengthen memory.
By Marianne Hayes