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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.=20 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.=20 They found that many of the cells in the hippocampus -- a region of the = brain important in learning and memory -- were marked by BrdU.=20 "Our results suggest that there is much more plasticity in the adult = primate 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."=20 For example, Alzheimer's and Parkinson's disease result from a = degeneration of nerve cells in the brain. If researchers can find a way = to stimulate nerve cell growth, it may help combat the effects of such = neurodegenerative disorders.=20 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.=20 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 (1998;95:3168-3171)=20