I thought many of you would find this interesting.
Jeff Nagelbush
[EMAIL PROTECTED]
Ferris State University
>>FOR IMMEDIATE RELEASE: 3 JANUARY 2001
>>Yale University
>>http://www.yale.edu/
>>
>>Interpretations of brain activity based on cognitive theories fail to
>>recognize
>>background neuronal firing
>>
>>New Haven, Conn. – When the brain is stimulated, functional imaging
>>results are
>>misinterpreted by neglecting the resting brain neurotransmitter activity,
>>a
>>study by a Yale researcher concludes. "There is an assumption made in the
>>use
>>of PET scans and functional magnetic resonance imaging (fMRI) that the
>>brain
>>works only when you give it a task to do," said Robert Shulman, Sterling
>>Professor of Molecular Biophysics and Biochemistry. "What I show here is
>>that
>>the brain works all the time. The brain at rest is doing the same sort of
>>neuronal firing as it does when stimulated by a task. Brain activity
>>slightly
>>increases when a task is performed and those increases are generally
>>assumed to
>>measure activity."
>>
>>Shulman, in a study published in the January issue of The American Journal
>>of
>>Psychiatry, said what this means can be seen by considering that the
>>brain’s
>>signal at rest is, for example, 100. Once it undertakes a task, the
>>brain’s
>>activity level rises by a small amount, say, from 100 to 101. "When we
>>look at
>>it pixel by pixel and subtract the activity of the brain at rest from that
>>during a task as is presently done, you would get this increment of one in
>>certain areas of the brain," he said.
>>
>>"The localized nature of imaging increments is accommodated readily by a
>>conception of the brain, based on cognitive psychology or cognitive
>>neuroscience, in which individual regions respond, like computer modules,
>>to
>>components of tasks selectively stimulated," Shulman said. "In this way,
>>images
>>are interpreted and experiments are planned in terms of a theory of mind,
>>and
>>are designed to extend the theory rather than to test it."
>>
>>In his article, Shulman reviewed recent research done with colleagues at
>>Yale
>>which enabled imaging results to be interpreted in terms of a specific
>>neuronal
>>activity, the release of the neurotransmitted glutamate. The glutamate
>>fluxes
>>showed that the resting brain, in the absence of explicit external
>>activity,
>>was actively transmitting information.
>>
>>Shulman said that his study offers hope of bridging two major divisions in
>>psychiatry -- those scientists who have a psychiatric view of the mind and
>>those with a neuroscientific view.
>>
>>"The ability to quantitate neurotransmitter activity both in the presence
>>and
>>absence of stimulation highlights and provides a criticism of the
>>psychological
>>assumptions behind the standard interpretation of images," he said.
>>"Instead of
>>allowing resting activity to be disregarded, as it is when the brain is
>>considered as a set of localized computers, it shows that resting activity
>>is
>>required for function and suggests ways in which more holistic theories of
>>mind
>>are supported by the imaging experiments."
>>
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