Magazine article Science News

Do Old Brain Cells Die?

Magazine article Science News

Do Old Brain Cells Die?

Article excerpt

Why do so many people become more forgetful as they age? For 2 decades, scientists have held to a simple, and therefore appealing, hypothesis: Age-related memory difficulties result from a gradual loss of cells in the hippocampus, a brain area long associated with memory formation and recall.

This notion first arose when rat studies showed that cell density in the hippocampus dropped dramatically during the late stages of a rodent's life.

Human studies seemed to confirm a similar age-related loss of brain cells.

In the last year, however, a small group of researchers has contested this view. "It's just plain not correct," says Peter R. Rapp of the State University of New York at Stony Brook.

This blunt challenge to dogma stems from a novel way of counting cells. While past studies tallied the number of brain cells in a thin slice of hippocampal tissue, the new method estimates the total number of hippocampal cells from counts of the cells in thick sections taken throughout the region.

A group headed by Mark J. West of the University of Aarhus in Denmark pioneered this technique and recently reported that the number of brain cells in the hippocampus differs little among young rats, old rats with good memory, and old rats with poor memory. Those results were criticized, however, because the group examined only a small number of animals and used a strain of rats different from that examined in most memory studies.

Rapp and Michela Gallagher of the University of North Carolina at Chapel Hill have now largely corroborated West's results in a study with a much larger number of rats. Moreover, they tested a rodent strain that's frequently used in age-related memory research.

Old rats, including ones that perform poorly in a memory-testing maze, have as many hippocampal brain cells as young rats, the two researchers report in the Sept. 3 Proceedings of the National Academy of Sciences. …

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