02.28.07

The brain is chaotic

Posted in you've got mail at 7:36 pm by nemo

From Chaos List-serv
New Study: The Brain is Chaotic

By Sara Goudarzi
LiveScience Staff Writer
posted: 27 February 2007
03:26 pm ET

The inner workings of the brain aren’t
as organized as once thought. According to a new study, it’s mayhem up
there.

It’s long been believed that information is passed on from one neuron
to another
at junctions where two neurons, or a neuron and a muscle, meet. Neurons are
nervous system cells that process and relay information.

At the junction of two neurons, also known as a synapse
, one neuron
releases a chemical messenger-neurotransmitter-to excite the other neuron.
This is done by diffusing the neurotransmitter to the branches (dendrites)
of the transmitting neuron.

The new study purports that neurons don’t just release these chemicals at
synapses but along the entire span of their extensions, all the while
exciting neighboring cells
.

Researchers studied white matter in the brains of rats. White matter makes
up the solid components of the brain that bridge the right and left
hemispheres. This part of the brain is responsible for transmitting
information because it’s mainly composed of nerve fibers that conduct
electrical impulses.

Because there are no synapses in the white matter, “it is not a place where
we would expect to see the release of messengers,” said Dirk Dietrich, a
study scientist from Bonn University.

However, when electrical impulses were sent through the transmission lines
of a neuron-known as axons
060321_axon_model_02.jpg&cap=A+simple+biophysical+model+of+an+axon+was+used+
to+study+the+catastrophic+consequences+of+free+radical+damage+to+neurons.+Th
e+result+was+that+the+axon+co> -the resulting neurotransmitter, glutamate,
didn’t just end up being released at the synapse.

“On their way through the gray matter
the axons probably
release glutamate at other points apart from the synapses,” Dietrich said.
“Nerve cells and dendrites are closely packed together here. So the axon
could not only excite the actual receptor but also numerous other nerve
cells.”

The findings, to be published in a forthcoming issue of the journal Nature
Neuroscience, could fundamentally change the notions that the brain follows
a specific ordered circuit and could have implications in medicine and
therapeutic drug options.

Source: LiveScience
http://www.livescience.com/humanbiology/070227_brain_chaos.html

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