EEG STUDY FINDINGS REVEALS HOW FWAR IS PROCESSED IN THE BRAIN
An estimated 8% of Americans will suffer from post traumatic stress
disorder (PTSD) at some point during their lifetime. Brought on by an
overwhelming or stressful event or events, PTSD is the result of altered
chemistry and physiology of the brain. Understanding how threat is processed in
a normal brain versus one altered by PTSD is essential to developing effective
interventions.
New research from the
Center for BrainHealth at The University of Texas at Dallas published online
today in Brain and Cognition illustrates how fear arises in
the brain when individuals are exposed to threatening images. This novel study
is the first to separate emotion from threat by controlling for the dimension
of arousal, the emotional reaction provoked, whether positive or negative, in
response to stimuli. Building on previous animal and human research, the study
identifies an electrophysiological marker for threat in the brain.
"We are trying to
find where thought exists in the mind," explained John Hart, Jr., M.D.,
Medical Science Director at the Center for BrainHealth. "We know that
groups of neurons firing on and off create a frequency and pattern that tell
other areas of the brain what to do. By identifying these rhythms, we can
correlate them with a cognitive unit such as fear."
Utilizing
electroencephalography (EEG), Dr. Hart's research team identified theta and
beta wave activity that signifies the brain's reaction to visually threatening
images.
"We have known
for a long time that the brain prioritizes threatening information over other
cognitive processes," explained Bambi DeLaRosa, study lead author.
"These findings show us how this happens. Theta wave activity starts in
the back of the brain, in it's fear center -- the amygdala -- and then
interacts with brain's memory center -- the hippocampus -- before traveling to
the frontal lobe where thought processing areas are engaged. At the same time,
beta wave activity indicates that the motor cortex is revving up in case the
feet need to move to avoid the perceived threat."
For the study, 26
adults (19 female, 7 male), ages 19-30 were shown 224 randomized images that
were either unidentifiably scrambled or real pictures. Real pictures were
separated into two categories: threatening (weapons, combat, nature or animals)
and non-threatening (pleasant situations, food, nature or animals).
While wearing an EEG
cap, participants were asked to push a button with their right index finger for
real items and another button with their right middle finger for
nonreal/scrambled items. Shorter response times were recorded for scrambled
images than the real images. There was no difference in reaction time for
threatening versus non-threatening images.
EEG results revealed
that threatening images evoked an early increase in theta activity in the
occipital lobe (the area in the brain where visual information is processed),
followed by a later increase in theta power in the frontal lobe (where higher
mental functions such as thinking, decision-making, and planning occur). A left
lateralized desynchronization of the beta band, the wave pattern associated
with motor behavior (like the impulse to run), also consistently appeared in
the threatening condition.
This study will serve
as a foundation for future work that will explore normal versus abnormal fear
associated with an object in other atypical populations including individuals
with PTSD.
This work was
supported by the Berman Laboratory of Learning and Memory at The University of
Texas at Dallas and the Jane and Bud Smith Distinguished Chair.
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