Working memory affected by aging
Reuters News

As people grow older, they often complain about having problems remembering what they did in the last few minutes, such as where they put their car keys. Now, thanks to the marvels of a modern imaging technique, scientists have been able to demonstrate where in the brain this deficit in very recent or "working" memory occurs.

The finding may lead to better ways to treat or prevent age-related memory loss, the researchers suggest.

Dr. Bart Rypma from the Hospital of the University of Pennsylvania in Philadelphia and colleague Dr. Mark D'Esposito of the University of California, Berkeley, report their results in the May issue of Nature Neuroscience. The team used functional magnetic resonance imaging (MRI) to look at specific brain areas of both young people and older folks as they attempted a memory task. This task consisted of looking at and then recalling sequences of letters. The study was designed to look at the brain during working memory "the kind... we use moment to moment in our everyday lives," Rypma told Reuters Health.

The study yielded several key findings, according to Rypma. "Older adults showed reduced activity relative to younger adults in one specific frontal brain region called the dorsolateral prefrontal cortex," he said.

The brain is divided into two hemispheres and consists of an outer layer of grey matter called the cortex, and an inner layer called white matter. Specific areas of grey matter are often referred to by names that describe their anatomic position, such as the prefrontal cortex, the most frontal part of the brain. 'Dorsolateral' refers to the back and sides of the prefrontal cortex.

Curiously, the team demonstrated that those subjects in the younger group who did best "showed less activity than those who performed poorly. But the opposite was true in older adults -- "those who performed more quickly and accurately showed more activity than those who performed poorly," Rypma explained, adding that "this difference only occurred during memory retrieval."

While the general findings of age-related difference in functioning centered on this area of the prefrontal cortex were anticipated, Rypma pointed out, the team did not expect to find "that better performing older adults showed more dorsolateral prefrontal activity than their poor-performing counterparts."

As to the practical significance of these findings, Rypma notes that contrary to the "general 'brain-rot' theory of aging... (these results) suggest aging may exert its effects on a specific brain region."

Rypma speculates that older study participants who did better on the tasks "may be those who have greater brain capacity to devote to memory retrieval." This increased capacity may be the result of a number of factors, including an increased supply of oxygen to the brain because of aerobic fitness.

He believes that the findings "will hopefully assist in targeting treatment strategies to assist older adults' failing memory. The exciting possibility is that effective treatment may come more from diet and exercise than from some sort of memory drug," he says.

Rypma plans to enlarge upon this research by looking at "to what extent our results generalize to other brain regions." In addition, he intends to look at how the differences in brain activation are related to speed.

"Behavioral research suggests that speed of performance may reflect the efficiency of mental processes," he explains, so "we would like to see if differences in brain activity don't reflect the efficiency of the brain processes that underlie those mental processes."

SOURCE: Nature Neuroscience 2000; 3:509-515.