Studies Find Brain Grows New Cells
by Gina Kolata in the New York Times
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For years, neurobiologists clung to a fundamental truth: once animals, or
people, reach adulthood, they may lose brain cells but they can never grow
new ones. There were a couple of exceptions -- in birds and rats -- but
the thought was that these were peculiarities of nature and not evidence
of a general principle.
But now, in experiments that experts call amazing, that dogma has been
overturned. Scientists have found that monkeys are constantly making new
brain cells in the hippocampus, an area of the brain used for forming
long-term memories. Moreover, they report, the production of new cells is
squelched when the animals are under extreme stress.
Experts say they fully expect that humans are no different and that they,
too, make new brain cells in adult life. That raises the glimmer of a
possibility of eventually treating degenerative disorders like Alzheimer's
or Parkinson's disease and injuries, like those resulting from stroke or
trauma, by prompting the brain to grow replacement cells, researchers
said.
It also means that neurobiologists must re-think their notions of how the
brain changes with learning or life experiences. The new study was by Dr.
Elizabeth Gould of Princeton University, Dr. Bruce S. McEwen of
Rockefeller University in New York and their colleagues. "It means that
there is a new mechanism for changing the organization of the adult
brain," said Dr. William Greenough, a psychologist at the University of
Illinois at Urbana-Champaign who studies learning and memory in rats. Dr.
Fred Gage, a neurobiologist at the Salk Institute in San Diego, said the
implications were "fabulously interesting."
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