Pain,
like beauty, is in the mind's eye. It is altered by
empathy and tempered by faith, three new brain-imaging
studies suggest. The bewitching effect of
belief can alter directly how strongly people feel
pain, causing measurable changes in brain cells and
synapses whether the torment is theirs or a loved
one's. The new findings, made public today by
independent research teams at the University of
Michigan, Princeton University, UCLA, and University
College London, offer the strongest evidence yet of
how the brain thinks about pain.
Mapping the neural anatomy of pain, the researchers
documented the ways in which the brain created a world
of its own from the raw material of physical
sensation. Using medical imaging scanners to monitor
brain activity, researchers at Michigan, UCLA and
Princeton revealed that simple faith in a placebo
could alter the neural circuits that process pain,
easing the agony.
In a separate experiment, the researchers at
University College showed that the brain was a mirror
of suffering, reflecting through many of the same
neural circuits the pain that others feel, much as
if the sensation were its own genuine torment. Indeed,
the brain's ability to share another's response to
pain at such a fundamental cellular level may be the
key to a sense of empathy, the personality trait that
underpins so many human relationships, researchers
said. "These brain regions are critical to the
interplay between the outside world and you,"
said neuropsychologist Helen Mayberg at Emory
University in Atlanta. By directly monitoring mental
activity, the researchers showed how expectations and
anticipation molded the brain's response to the
physical sensation of pain. To a certain degree, pain
is an act of imagination. "We are zeroing in on
some pathways where our thoughts and beliefs are
changing our physical and emotional experience,"
UCLA psychologist Matthew Lieberman said. "We
don't typically think of those as things we can
control." Each team used brain mapping techniques
to survey the same neural terrain from three slightly
different perspectives.
Two of the studies were published today in the journal
Science. The third will be published next month in
Neuroimaging. To better understand pain and empathy, a
team led by social psychologist Tania Singer at the
Institute of Neurology at University College tested 19
couples who, because they were romantically involved,
could be expected to be attuned to each other. One
woman from each pair was monitored with a functional
magnetic resonance imaging scanner. Her neural
activity was recorded first as researchers gave her a
brief electric shock, then as her partner received the
same shock. The researchers discovered that the same
critical brain regions involved in processing the
physical sensation of pain were activated in each
case. Feelings of empathy for another's pain triggered
regions of the brain responsible for processing pain,
much as if it were a direct sensation, researchers
discovered.
To Singer and her colleagues, it strongly suggested
that humans were hard-wired for empathy."We are
pretty sure that it is a universal mechanism,"
Singer said. "It is how we can put ourselves
emotionally in another's shoes." To investigate
how belief affects the brain's response to pain,
Lieberman and his UCLA colleagues conducted brain
scans of 14 patients given a placebo to treat their
chronic abdominal pain. The experiment revealed that
the patients' faith in the substance they were given
eased their symptoms and also produced physical
changes in areas of the brain that processed pain.
The greater the brain changes, the greater the reduction
in pain, the researchers determined.
At Michigan and Princeton, researchers produced even
more compelling evidence that the expectation of
relief caused physical changes in how the brain
handled pain. They tested dozens of volunteers by
giving them shocks while monitoring their neural
activity in a brain scanner. Then researchers gave
all the volunteers a placebo in the form of a harmless
cream the patients were told would prevent the pain.
Then the scientists conducted another round of shocks.
The expectation of relief was enough to cause physical
changes in those pain-processing areas of the brain,
offering evidence of the placebo effect. "We
actually see physical changes in the brain that
correspond closely to changes in symptoms that the
patients report," said psychologist Tor Wager,
who led the Michigan research team. The researchers
determined that pain depended not only on the actual
sensory signals from nerves that the brain received
but also on a person's emotional state.
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