Primates Grow Nerve Cells In Brain

NEW YORK (Reuters) -- The brains of adult monkeys do generate new
nerve cells, a process once thought to be impossible. And that process
can be inhibited by psychological stress, according to a report in the
Proceedings of the National Academy of Sciences.

Dr. Elizabeth Gould, of Princeton University in New Jersey, and
colleagues injected six adult male marmoset monkeys with BrdU, a
chemical taken up by cells that are dividing. The brain tissue was
examined either 2 hours or 3 weeks after the procedure.

They found that many of the cells in the hippocampus -- a region of the
brain important in learning and memory -- were marked by BrdU.

"Our results suggest that there is much more plasticity in the adult
brain, and potentially in the adult human brain, than was previously
believed," Gould told Reuters. "Because the hippocampal formation is
involved in learning and memory, it's very likely that these new neurons
participate in learning and memory. That has tremendous implications for
understanding age-related cognitive decline and diseases that are
associated with learning and memory impairments."

For example, Alzheimer's and Parkinson's disease result from a
degeneration of nerve cells in the brain. If researchers can find a way
stimulate nerve cell growth, it may help combat the effects of such
neurodegenerative disorders.

Immediately prior to injection with BrdU, some of the monkeys were
individually placed into the cage of an unfamiliar adult male monkey and
left there for 1 hour. The research team found that the brains of these
monkeys showed significantly fewer BrdU-marked cells than brains of
monkeys who were not exposed to the stressful situation.

It's not clear why this occurs, according to the report. But the finding
may explain why people with recurrent depressive illness and
post-traumatic stress disorder show a reduction in hippocampus volume
on magnetic resonance imaging scans, the authors wrote.

SOURCE: Proceedings of the National Academy of Sciences

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