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--></style><title>Physics colloquium tomorrow (May 6): Brain
Imaging</title></head><body>
<blockquote type="cite" cite align="center"><font size="+1"><b>Imaging
the Addicted Brain: From Molecules to Behavior</b></font></blockquote>
<blockquote type="cite" cite align="center"><b>Dr. Nora Volkow<br>
Director, National Institute on Drug Abuse<br>
<br>
Thursday, 5/6/2004<br>
Time: 4:15pm</b></blockquote>
<blockquote type="cite" cite align="center"><b>Place: Room
10-250</b><br>
<b></b></blockquote>
<blockquote type="cite" cite align="center"><br></blockquote>
<blockquote type="cite" cite><u>ABSTRACT:<br>
</u>Imaging technologies such as positron emission tomography (PET)
and magnetic resonance imaging (MRI) have provided tools and have
identified new challenges to study the effects of drugs of abuse on
the human brain. Imaging studies have revealed neurochemical and
functional changes in the brains of drug-addicted subjects that
differentiate them from drug- intoxicated subjects and provide new
insights into the mechanisms underlying addiction. <br>
<br>
Neurochemical studies have shown that the large and rapid drug-induced
increases in dopamine found in the brain during drug intoxication are
associated with the reinforcing effects of abused psychoactive drugs.
By contrast, after chronic drug abuse and during withdrawal, brain
dopamine function is markedly decreased and these decreases are
associated with dysfunction of prefrontal brain regions (including
orbitofrontal cortex and cingulate gyrus). Such changes have
been shown to result in decreased sensitivity to natural reinforcers
(dopamine also mediates the reinforcing effects of natural
reinforcers) and in disruption of frontal cortical functions, such as
inhibitory control (ability to control impulses or desires) and
salience attribution (ability to assign reinforcing value to
stimuli). <br>
<br>
Functional imaging studies have shown that during drug intoxication or
during craving, these frontal regions get activated as part of a
complex pattern that includes brain circuits involved with reward
(nucleus accumbens), motivation (orbitofrontal cortex), memory
(amygdala and hippocampus), and cognitive control (prefrontal cortex
and cingulate gyrus). This presentation will focus on some recent
findings from neuroimaging studies that have broadened our
understanding of drug abuse and addiction in particular, and brain
science in general.<br>
</blockquote>
<blockquote type="cite" cite>Physics Colloquium Series<br>
Physics Headquarters, 6-113<br>
(617)253-6259 FAX (617)253-8554<br>
<a
href="http://web.mit.edu/physics/">http://web.mit.edu/physics/</a></blockquote>
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<div>Stu Dietz<br>
Biology Education Office, Rm. 68-120<br>
Massachusetts Institute of Technology<br>
77 Massachusetts Ave.<br>
Cambridge, MA 02139<br>
<br>
Phone (617) 252-1783<br>
Fax (617) 258-9329</div>
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