(Philadelphia, PA) -- Using a novel application
of an fMRI (functional magnetic resonance imaging) technique, researchers
at the University of Pennsylvania School of Medicine
have, for the first time, visualized the effects of everyday psychological
stress in a healthy human brain. Their work, performed at Penn's
Center for Functional Neuroimaging, provides a neuro-imaging marker
of psychological stress -- which will pave the way for the development
of improved strategies for preventing or correcting the long-term
health consequences of chronic stress. The researchers' study appears
in the November 21 online edition of Proceedings of the National
Academy of Sciences.
the Penn study, researchers induced stress on healthy subjects by
asking them to quickly tackle challenging mental exercises while
being monitored for performance. During the fMRI scans, the researchers
also recorded subjects' emotional responses -- such as stress, anxiety,
and frustration -- and measured the corresponding changes in stress
hormone and heart rate. Many subjects described themselves as being
"flustered, distracted, rushed and upset" by the stress
The results showed increased cerebral blood-flow during the "stress
test" in the right anterior portion of the brain (prefrontal
cortex) -- an area long associated with anxiety and depression.
More interestingly, the increased cerebral blood-flow persisted
even when the testing was complete. These results suggest a strong
link between psychological stress and negative emotions. On the
other hand, the prefrontal cortex is also associated with the ability
to perform executive functions -- such as working memory and goal-oriented
behavior -- that permit humans to adapt to environmental challenges
and threats. "The message from this study is that while stress
may be useful in increasing focus, chronic stress could also be
detrimental to mental health," concludes Jiongjiong
Wang, PhD, Assistant Professor of Radiology and principal
investigator of the study.
"How the brain reacts under psychological stress is an untouched
subject for cognitive neuroscientists, but it is certainly a critical
piece of the puzzle in understanding the health effects of stress,"
adds Wang. "Our findings should help significantly advance
our understanding of this process."
date, most fMRI studies have indirectly measured changes in cerebral
blood-flow and metabolism induced by neural activation, using a
technique that is sensitive to the oxygenation levels in blood.
“The fMRI technique employed in our study – arterial
spin labeling – can measure cerebral flood-flow directly,”
states John A. Detre, MD, Associate Professor of
Neurology and Radiology, and senior author of the study. “This
technique is very similar to PET (positron emission tomography)
scanning, except that it’s entirely non-invasive – without
the need for injections or radioactivity. In this elegant technique,
water molecules in subjects’ own blood are ‘tagged’
by the magnet and used as the natural contrast agent to measure
cerebral blood-flow.” Researchers at Penn’s Center for
Functional Neuroimaging have been at the forefront of the development
of this technique, and its applications to imaging brain-function
during cognitive and emotional processes.
The study was sponsored by grants from the National Science Foundation,
the National Institutes of Health, and the U.S. Air Force. In addition
to Drs. Wang and Detre, the team of investigators included Penn
researchers Hengyi Rao, Gabriel S. Wetmore, Patricia M.
Furlan, Marc Korczykowski, and David F. Dinges.
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