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Washington,
November 16: An Indian-origin researcher and his
colleagues have proposed a new theory of brain
flexibility, which helps explain how the brain
compensates for damage from injuries caused by stroke or
Alzheimer's.
Stanford postdoctoral fellow
Sashank Varma and Carnegie Mellon University
neuroscientist Marcel Just's theory is called 4CAPS, an
acronym for Capacity Constrained Concurrent Cortical
Activation-based Production System.
The theory
suggests that various brain areas volunteer themselves
when their strengths are called for, and that they
permit less efficient but capable areas to step forward
when a specialised area gets injured or disabled, as may
occur as a result of a stroke.
The researchers
have made a number of computational models to
demonstrate this process, such as a model that
understands English sentences.
They say when a
stroke damages the part of the brain involved in
language processing called Broca's area, located in the
left prefrontal cortex, the corresponding site on the
right side of the brain often becomes activated during
language processing, even within hours after a
stroke.
According to the theory, the same dynamic
allocation mechanism that allows brain areas to
volunteer themselves on a moment-by-moment basis would
also come into play if Broca's area were damaged, and
would allow any excess computational load to spill over
to the right hemisphere mirror site on a more permanent
basis.
The researchers also suggest that upon
damage to some brain areas as a result of Alzheimer's
disease, additional "helper" areas start performing such
tasks as they normally do not perform in people without
the disease.
"Many brain-imaging studies have
shown as the nature of the task changes, so does the set
of activating brain areas. It is as though substitutions
of team players are being made dynamically in response
to changes in the game," said Just, the D.O. Hebb
Professor of Psychology.
"We credit this dynamic
mechanism with the fluidity or adaptability of human
intelligence, and with much of the plasticity that
occurs with learning or with recovery from brain
damage," Just added.
The researchers say that the
4CAPS theory provides a framework for scientists and
medical researchers to better understand nascent topics
in neuroscience, such as how brain areas communicate and
collaborate with one another during the thought process
and how this can go awry.
It also provides an
account of what limits our ability to do
multitasking.
"The thousands of facts that
scientists have learned from brain imaging studies cry
out for some sort of organization, some way to impose
coherence, and ultimately to understand the brain system
that is producing the results. The theory provides a new
conceptual framework for understanding how the fluidity
of thought arises from the dynamics of brain activity,"
Just said.
"As neurological issues arise in
education, aging and development, and as a basis for a
knowledge-based economy, it will become increasingly
important that human brain function be understood by
students, parents and educators, patients and doctors,
trainees and managers, citizens and policy-makers," Just
added.
The researchers have described their
theory in a paper published in the journal Cognitive,
Affective, and Behavioral Neuroscience.
(ANI)
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