Brain Changes as We Age
Of course, no one denies that the brain, like the rest of the body, does change with age. Most researchers accept the notion that as people get older, they experience a general decline in the speed with which they perform various cognitive tasks. However, procedural memory (which involves things we do without thinking, like knowing how to read or making quick associations) generally tends to resist aging and diseases of the brain, according to Gordon. Working memory -- which centers on processing, storing, and recalling information -- and episodic memory, which entails recalling a recent past experience, seem to erode more quickly. For example: You look up a phone number but are interrupted before you make the call. Remembering the number after the interruption would be a successful use of working memory. Episodic memory is being able to remember what you had for breakfast or what route you took home yesterday.
A number of neuroimaging studies back up these assertions. Scans of older adults show gradual tissue loss, or declines in tissue densities, in the frontal, temporal, and parietal regions of the brain, which are all involved in working and episodic memory. Other imaging studies have shown decreased (or alterations in) activity in the left frontal cortex, which is involved in working memory processing. Researchers at the University of Edinburgh have found that age-related abnormalities in the white matter -- the substance that transfers information between different regions of the brain -- are also linked with such health problems as hypertension. This suggests that such abnormalities might be preventable, at least to the extent that high blood pressure and other circulatory problems can be controlled. Although the significance of these defects is unclear, having many of them has been associated with cognitive decline.
Still, the Scottish study and others, like the Seattle Longitudinal Study of Adult Intelligence, show that aging deficits tend to be small and gradual. In the Seattle study, declines in a range of cognitive abilities were generally not seen before age 60, and by the time subjects reached 74 only small changes were observed. Even at age 81, less than half of the adults showed significant declines over the previous seven years.
