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by Chris Morrison, sciencefriday.com
staff
The way that neuroscientists look at most of our
brain may be changing. Glia, small cells that
drastically outnumber their larger neighbors in the
brain, neurons, account for about half the brain's
weight. Traditionally, they have been characterized
as mere support cells for the brain's neural
network, which sends electrical impulses along
complex routes to form the cellular basis for
thought, learning and memory. But now, scientists
are finding that glial cells may play a much
greater role in the brain's communication than
previously thought, according to a recent report in
the Journal of Neuroscience.
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The larger objects in the picture are
neurons . The smaller objects are
the long underrated glial cells.
(larger
view)
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Eric Newman and Kathleen Zahs, physiologists at
the University of Minnesota, have worked with rat
retinas to show that when glia are prodded, (or
"stimulated mechanically"), they can release
calcium--which can then influence communication
between neurons. The calcium ions emitted by one
glial cell can trigger surrounding glia to release
calcium too, spreading a signal outwards like a the
ripples caused by throwing a stone into a pond.
"The calcium wave releases glutamate from the
glial cells," said Newman. "We're not sure how it
happens, but it has a direct impact on the firing
of the neurons." Glutamate is a neurotransmitter, a
chemical used by neurons to communicate with each
other.
Newman and Zahs showed that more than half of
the neurons exposed to the glutamate from glial
cells changed either the speed or magnitude of
their firing. Newman cautions that the results,
although very interesting, have yet to be seen in a
live animal model, although he is optimistic that
those results will be similar. Newman said that
tests using the natural stimulus of the retina, a
flashing light, are needed to determine if the
phenomenon occurs in animal models, and not just
when the glial cells are poked by inquisitive
researchers.
See
the calcium wave and hear neurons firing!
Neuroscience
for Kids
American Academy of
Neurology
Whole
Brain Atlas
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