Picture yourself in a
medical office, anxiously awaiting your annual flu shot. The nurse casually
states, “This won’t hurt a bit.” But when the needle pierces your skin it
hurts, and it hurts a lot. Your expectations have been violated, and not in a
In a study published in the early online edition of the
journal PAIN, researchers at Wake Forest Baptist Medical Center have identified
through imaging the part of the brain that is activated when a person expects
one level of pain but experiences another.
“This finding gives us a better understanding of the
importance of how our expectations of pain affect the experience of pain,” said
Fadel Zeidan, Ph.D., assistant professor of neurobiology and anatomy at Wake
Forest Baptist and first author of the study. “This effect shows us how
important it is to manage people’s expectations when it comes to pain.”
Previous studies have shown that the expectation of
intense pain can make pain feel worse while the expectation of milder pain can
make it hurt less. However, the brain mechanisms associated with processing
mismatches between expected and experienced pain have been poorly understood.
This Wake Forest Baptist study found that activation of
the parietal lobe and insular cortex are involved in processing real-time
mismatches between expected and experienced pain.
First, 15 healthy participants were trained to expect
mild or intense levels of pain when showed visual cues of the words “low” and
“high.” Heat was applied to the participants’ legs with thermal probes. The
heat stimuli -- 47 degrees C (116.6 F) or 50 degrees C (122 F) -- were designed
to elicit markedly different experiences of pain intensity. Participants used a plastic sliding scale to
indicate pain intensity and unpleasantness.
Next, the participants underwent functional neuroimaging
scanning to measure their brain activity while they received the different
levels of heat following both correct and incorrect cues.
Brain activity during the exact moment when the subjects
realized the cues were incorrect was identified. This allowed the researchers
to assess how the experience of pain overrides the very powerful influence of
expected pain when there was a difference between cues and ensuing thermal
“We found that multiple regions within the left posterior
parietal cortex are differentially engaged when the expectation of an impending
painful stimulus is violated,” said the study’s senior author, Robert Coghill,
Ph.D., director of anesthesiology research at Cincinnati Children’s
Hospital. “These brain regions also have
been found to be associated with violated expectations to visual, auditory and
These findings demonstrate that the powerful influence of
expectations on the subjective experience of pain can be dramatically altered
when there is a substantial difference between expected and experienced pain.
“Knowing how vital trust is to the doctor-patient
relationship, we hope these findings will help physicians and other caregivers
have a better understanding of the importance of how what patients expect
affects their experience of pain,” Zeidan said.
This work was supported by the National Institute of
Neurological Disease and Stroke and the National Center of Complementary and
Co-authors include Oleg V. Lobanov, M.D., Ph.D., of
Washington University in St. Louis and Robert A. Kraft, Ph.D., of Wake Forest