Researchers now have an unprecedented wealth of data on the aging brain from the Seattle Longitudinal Study, which has tracked the cognitive abilities of thousands of adults over the past 50 years. These results show that middle-aged adults perform better on four out of six cognitive tests than those same individuals did as young adults, says study leader Sherry Willis, PhD, of the University of Washington in Seattle.
While memorization skills and perceptual speed both start to decline in young adulthood, verbal abilities, spatial reasoning, simple math abilities and abstract reasoning skills all improve in middle age.
For example, psychologist Cheryl Grady, PhD, of the University of Toronto, and her colleagues have found that older adults use more of their brains than young adults to accomplish certain tasks. In a study published in the Journal of Neuroscience (Vol. 3, No. 2) in 1994, Grady reported that performing a face-matching task activates mainly the occipital visual areas in younger adults, but older adults use these areas as well as the prefrontal cortex. (Both groups of adults are equally skilled at the task.)
Several groups, including Grady’s, have also found that older adults tend to use both brain hemispheres for tasks that only activate one hemisphere in younger adults. Younger adults show similar bilateralization of brain activity if the task is difficult enough, Reuter-Lorenz says, but older adults use both hemispheres at lower levels of difficulty.
The strategy seems to work. According to work published in Neuroimage (Vol. 17, No. 3) in 2002, the best-performing older adults are the most likely to show this bilateralization. Older adults who continue to use only one hemisphere don’t perform as well.