However, the news isn't all bad, say researchers at the University of Toronto, who have devised a test to measure memory changes in healthy people as they get older.
"Aging causes subtle, neurobiological changes in the frontal lobe that may reduce processing power, so that younger adults will be able to give more specific information about an event than older people," says Eva Svoboda, a doctoral student at the Rotman Research Institute and co-author of a new study on the subject.
"But older people have the ability to relate more general information acquired over a lifetime and to integrate the event into their lives," she says. "The idea that with age comes wisdom is valid."
Svoboda and her colleague and study leader Brian Levine, a neuropsychologist, studied 15 younger and 15 older adults to analyze how each group recalled specific events in their past. The researchers' purpose was to devise a standard test to measure the changes in memory processing as healthy people age. The test, called "The Autobiographical Interview," could then be used to assess memory loss in people with dementia or who have had strokes, tumors or traumatic injuries.
The results of their study appear in the December issue of Psychology and Aging.
In the study, the researchers asked the 15 younger adults, aged 19 to 34, and the 15 healthy older adults, aged 66 to 89, to recall personal events from five different periods of their lives: early childhood; their teenage years; early adulthood; their middle years; and the previous year. The people could talk about anything, and recollections included a first kiss, breaking a leg in a sledding accident, the birth of a child, the death of a parent or grandparent, being punished in school by a teacher, and leaving Germany during the Nazi occupation.
The remembered events were evenly balanced between good and bad memories, Svoboda says.
The recollections were then analyzed word for word using a new scoring method that distinguished between specific information about an event, and more general facts that related the event to other information.
Specific facts were those that were "limited to time and place," Svoboda says. They comprised the bare facts of a situation -- what the person wore, how they felt at the moment, the visual scene, exactly what happened.
General details weren't limited by time and included facts about how the event represented a phase in a person's life, or information about what was going on in the world at the time, such as Hitler's rule in Germany.
"Older people overall had more trouble recalling specific events. They might not have remembered what time of day something happened, or wouldn't give as much detail about their surroundings," Svoboda says.
The tendency for older people to give more general responses than younger adults was true even in follow-up questions designed to elicit more specific details.
"Older people still gave less details and lots more general information," she says.
Svoboda says that if you put this information into the "hunter-gatherer" context of human evolution, these age-related memory changes make sense.
Younger, stronger adults who may be hunters, for example, need to be alert to specific facts -- where an animal is, where it is going, and the sights and smells of the environment that will guide the person in the hunt. However, older people, no longer able to hunt, can provide contextual information about the animals, knowing from past experience where they most likely will congregate at certain times of the year, Svoboda says.
"The older person could be the wise person in the tribe who's been around a long time and who has a vast amount of information to offer," she says.
The researchers are also beginning to use their test as a tool to assess memory loss in ill people. Their theory is that traumatic injuries resulting in frontal lobe damage causes an exaggerated version of the pattern seen in aging.
"We are testing people with frontal lobe damage, and so far the test looks good as a diagnostic tool," she says.
Dr. Dean K. Shibata, a radiologist at the University of Washington who studies imaging of brain damage, says "it's an interesting idea that the brains of people with lesions would simulate older people's brains. But 'exaggerated version' is an appropriate description because in a trauma you destroy so much more of the brain than happens in aging."
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