X-Message-Number: 11311
Date: Tue, 23 Feb 1999 15:54:18 -0500
From: Jan Coetzee <>
Subject: Exercise: brain cells

Exercise, variety stimulate brain cells

NEW YORK, Feb 22 (Reuters Health) -- Studies in mice suggest that
vigorous exercise may
stimulate the development of new cells in the area of the adult brain
involved in learning. The
study findings also suggest that exercise and interesting, varied
surroundings may prolong the
life of these cells.

These results indicate that the replacement of cells in this area,
called the hippocampus, ``may
be regulated by experience,'' according to Dr. William Greenough and
colleagues at the
University of Illinois in Urbana. Their comments come in response to two
studies published in
the March issue of the journal Nature Neuroscience.

Until recently, scientists believed that the number of mammalian brain
cells remained static
once the brain matures. But researchers have since discovered cell
generation in the brains of
adult mice, birds, and monkeys. This cell regeneration seems to be
limited to the brain's
hippocampus, a center for memory and learning.

Both studies sought to determine the living conditions most conducive to
this regenerative

In one study, investigators at The Salk Institute for Biological Studies
in La Jolla, California,
used fluorescent staining techniques to identify newly-formed brain
cells in the hippocampi of
mice. They placed these mice in various living environments, and had
them perform specific

The authors found that ``voluntary exercise in a running wheel increased
cell proliferation,''
doubling the number of surviving newborn cells in the hippocampus.

The team's findings appear to fit with what experts know about the
hippocampus. In their
commentary, Greenough and his colleagues speculate that ``intense
exercise in a natural
environment may be associated with a need for increased navigation
skills.'' The hippocampus
is thought to be the 'control center' for the learning processes
involved in understanding and
navigating the physical world.

In a second study, researchers at Princeton University and Rutgers
University, both in New
Jersey, used similar methods to study new brain cells in mice exposed to
various living
conditions. They report that ``environmental complexity increases the
number of adult-generated
hippocampal neurons in... mice.'' In other words, mice exposed to living
spaces filled with
interesting, varied objects and stimuli had higher cell regeneration
than rodents placed in stark,
empty cages.

The New Jersey researchers theorize that ``learning about space... has a
highly trophic
(growth-inducing) effect on adult generated hippocampal neurons.'' And
they point out that
immature neurons are especially suited to make the quick, novel
connections necessary in
spatial learning.

Greenough and colleagues speculate that the hippocampus has developed
the ability to
regenerate in order to aid the cerebral cortex ``by adding neurons that
can deal with new
information (while) deleting those that encode obsolete information.''

SOURCE: Nature Neuroscience 1999;2:203-205, 260-265, 266-270.


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