Tuesday, 29 January 2013
Sleep and Short-Term Memory
Old people regularly lament our short-term memory lapses and we often do it with rueful jokes as if we are whistling past the graveyard of brain cells. An example from a story here in 2009 when I lived in Maine:
”ITEM: I go the kitchen for a glass of water. I am momentarily distracted because the cat wants a pet and then I return to the library before I recall that I am thirsty.
“ITEM: I bundle myself into my winter outdoor gear and walk the six blocks to the local mini-grocery for a single item – a loaf of their excellent sour dough bread. While I’m there, the owner offers me a taste of a new cheese he has received. I buy a chunk and return home without the bread...
“Basically, these days, I do many things twice,” I wrote, in an attempt to lighten the fear too many of such incidents incur.
In the four years since I posted that, my short-term memory has gotten even shorter. It appears now that it is possible, in the second or two it takes to pick up a pen, to forget what the reminder is that I had intended to jot down.
That quote above was the lead-in to a study I was reporting that compared the memories of young and old people and showed, said the researchers, that elder brains have trouble ignoring extraneous information which results in overload and, therefore, dropped bits of information.
It was a reassuring study implying that if elders focused more carefully and indulged in less multi-tasking, our forgetfulness might be alleviated or, at least, reduced.
Now comes a new young/old brain study reported in The New York Times on Sunday suggesting something different:
”...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.”
Alarmingly, those “structural brain changes” involve loss of brain tissue [emphasis is mine]:
”In the study, the research team took brain images from 19 people of retirement age and from 18 people in their early 20s. It found that a brain area called the medial prefrontal cortex, roughly behind the middle of the forehead, was about one-third smaller on average in the older group than in the younger one — a difference due to natural atrophy over time, previous research suggests.”
The tests involved word memorization. Each age group was asked to recall the same sets of words and after about 25 minutes, the young group outscored the old group in recall by about 25 percent. But the bigger difference occurred after a night's sleep:
”On a second test, given in the morning, the younger group outscored the older group by about 55 percent.
“The estimated amount of atrophy in each person roughly predicted the difference between his or her evening and morning scores, the study found. Even seniors who were very sharp at night showed declines after sleeping.
“The analysis showed that the differences were due not to changes in capacity for memories, but to differences in sleep quality.”
Nothing can be done about the pre-frontal brain atrophy, but there may be other options:
”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...
“...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 the director of the cognitive neuroscience program at Northwestern University, who was not involved in the research.”
I hope you noted the important reference to exercise in the last paragraph.
I try to counter my short-term memory holes with lists and to a reasonable degree, they work. It's those five-second walks from one room to another during which the goal disappears from my brain that are most irritating.
I'd sure like to find some that electrical stimulation therapy to improve my sleep.
At The Elder Storytelling Place today, Marc Leavitt: Proof of Age