http://www.dukenews.duke.edu/pnas.html
Duke University - Duke News Service
MRI Studies Provide New Insight Into How Emotions Interfere With
Staying Focused
DURHAM, N.C. -- Duke University researchers have shown how emotions
such as fear or horror travel along separate paths through the brain
and are more likely than simple distractions to interfere with a
person's efforts to focus on a task such as driving.
Using functional MRI to watch human brains in action, the researchers
showed that emotional stimuli and "attentional functions" like driving
move in parallel streams through the brain before finally meeting up
in a specific part of the brain's prefrontal cortex.
The results, published in the August 20 issue of The Proceedings of
the National Academy of Sciences (PNAS), help explain why a person who
suddenly feels a pang of emotion is especially likely to lose focus.
They also may lead to new avenues of research for treating depression,
attention-deficit disorder, post-traumatic stress syndrome and other
disorders.
"We've known for a long time that some people are more easily
distracted and that emotions can play a big part in this," said Kevin
S. LaBar, assistant professor at Duke's Center for Cognitive
Neuroscience and an author of the study. "Our study shows that two
streams of processing take place in the brain, with attentional tasks
and emotions moving in parallel before finally coming together." The
two streams are integrated in a region of the brain called the
anterior cingulate, which is located between the right and left halves
of the brain's frontal portion and is involved in a wide range of
thought processes and emotional responses.
LaBar and his colleagues used functional MRI devices to study the
brains of neurologically healthy subjects who tried to pay attention
to specific visual targets on a screen. The test subjects were
distracted in various ways, sometimes by images that were likely to
evoke an emotional response. The results confirmed previous findings
that emotional stimuli are more likely to cause a person to lose
focus. However, they also shed light on the long-standing mystery of
how the brain juggles different kinds of signals, and how the signals
travel.
The Duke study indicates that the brain segregates attentional and
emotional functions into parallel streams that extend into the
prefrontal cortex. Emotional processing tends to occur in the ventral,
or lower, part of the brain's front, while attentional tasks occur
near the top. Surprisingly, an increase in one type of function is
accompanied by a noticeable decrease in the other.
"This study is part of our larger effort to identify parts of the
brain that are associated with emotional processing," said Gregory
McCarthy, director of the Duke-University of North Carolina Imaging
and Analysis Center, who headed the research study. "These findings
are important because diseases that involve distractability, from
Alzheimer's to attention-deficit disorder, always seems to involve the
prefrontal cortex. Understanding the biology of this will speed
efforts to develop drugs or therapies that may influence these
systems."
The research team is now carrying out a similar study with subjects
diagnosed with clinical depression to see how their brain activity
might differ. The study reported in PNAS was supported by the
Department of Veterans Affairs, the National Institute of Mental
Health, the National Alliance for Research on Schizophrenia and
Depression and the Japan Foundation for Aging and Health.
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