Keeping aging minds sharp

More than 100 years ago, American humorist Mark Twain described the shortcomings of memory and aging this way: "When I was younger, I could remember anything, whether it happened or not," Twain quipped. "But my faculties are decaying now," he added, "and soon I shall be so I cannot remember any but the things that never happened."

In recent years, Henry L. Roediger III, PhD, of Washington University--a presidential invited speaker at APA's 2003 Annual Convention in Toronto--has used Twain's witticism to describe his and others' findings in memory and aging. Hundreds of studies now prove Twain's contention that young and old alike recall things that never occurred, while newer studies reveal that old people are in fact more likely than the young to lose their memory for actual events and to remember things that didn't happen.

But research just out of the lab suggests that the beloved satirist may have been wrong in a key detail, said Roediger in his convention speech. In three as-yet unpublished studies, he and colleagues demonstrate that memory decline is not an inevitable consequence of aging--that for a particular subset of older adults, memory skills are as sharp as a 20-year-old's.

Frontal lobe functioning

Roediger and researchers at Washington University and the University of New Mexico embarked on this new line of study in an effort to explain why older people--and more strikingly, those with Alzheimer's disease--show the memory declines that Twain described.

They posited that deficits in frontal-lobe functioning may in part be the culprit, as current science holds that the frontal lobes shrink as we age, and their deterioration is responsible for global aging processes, including loss of memory and attentional control.

As the frontal lobes decrease in size, older people have a harder time distinguishing between what they've actually seen on a memory task--a skill known as "source monitoring"--and private, if related, thoughts.

Based on these findings, Roediger's team reasoned that adults with the lowest frontal-lobe functioning should show greater false recognition of items than those with higher frontal-lobe functioning.

The researchers launched a series of memory studies to test the notion, first separating older adults who were high or low in frontal-lobe functioning using a test battery designed for the purpose. (Younger adults who take the battery uniformly show high frontal-lobe functioning, Roediger noted.)

In the first study, "high-frontal" seniors, "low-frontal" seniors and younger adults tried to recall whether they had seen a particular word in a list of related words--"sleep" in a list containing "bed," "rest" and "awake," for example.

In a second study, they tried to recall words from a list related to a single theme, where the five most common words in the category are omitted but nevertheless prompt a memory association.

In a third experiment, participants viewed videos of fabricated crimes, such as a workman stealing a wallet from an office desk. They later received a narrative of the event, which in some cases contained errors in detail. They were then tested on the narrative and on what they'd seen on the video, giving researchers a chance to gauge their source-monitoring ability.

All three paradigms showed the same striking results: While low-frontal adults uniformly performed poorly compared with younger adults, "high-frontal older adults' data looked just about like the young adults," said Roediger--meaning roughly a quarter of the older sample showed this pattern.

Why some older adults are blessed with this capacity is still a mystery, Roediger added. Many older people express hope that their ability to solve that much-vaunted memory device--the crossword puzzle--proves their memory mettle, but unfortunately it is not the case, he said.

"We know that older adults who do crossword puzzles do better on all sorts of cognitive tests than others, but we don't know cause and effect," Roediger said. "It could be they do crossword puzzles because they still can, not that the puzzles make them sharper." Still, he said, "I tell them it can't hurt."