Research Supports Idea That Age Doesn't Hinder Learning ; Findings Reported Today Give Evidence That a Key Part of the Brain

Article excerpt

For most of this century, scientists have believed that the human brain grew until a certain age, then stopped - making learning more difficult in later years.

Now, researchers have the clearest evidence yet that the part of the brain most closely associated with complex learning and memory continually regenerates itself.

On one level, the findings reported in today's issue of the journal Science may help researchers working on treatments of brain damage or brain diseases, as well as ways to stimulate learning.

But on a more basic level, they suggest that the mental failings once assumed to be an unavoidable pitfall of aging are little more than stereotypes and have no basis in biological fact.

"There is a new sense of possibilities and hope," says Paul Grobstein, a neurobiologist at Bryn Mawr College in Pennsylvania. "The biology validates that."

Scientists have been building toward this conclusion for several decades. The model of the static brain began to crumble as early as the mid-1960s and early '70s, when experiments showed that the nervous systems of slugs and other animals demonstrated the ability to change their structure over time by altering their network of brain cells.

Subsequent experiments turned up evidence of the generation of new brain cells - a process called neurogenesis - in adult rats, mice, dogs, and other lower-order mammals. In this decade, scientists have also found neurogenesis in several types of adult monkeys and even in adult humans. But these findings were confined to less evolved, older portions of the brain that are believed to play a less-crucial role in the highest brain functions.

Despite this evidence, many neurologists continued to believe that neurogenesis did not exist in the cerebral cortex of higher- order primates and humans. Their feeling was that the stability of the cerebral cortex was crucial to memory and identity, both of which require a strong degree of constancy.

"People thought: If the cerebral cortex is important in memory, how could it change?" says Charles Gross, a professor at Princeton University in New Jersey and one of the study's authors. …


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