Studies map mind's role in experience of pain
Brain scans show faith, empathy measured affect pain perception

Friday, February 20, 2004

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 their own or a loved one’s.

The new findings, to be made public today by independent research teams at the University of Michigan, Princeton University, the University of California at Los Angeles 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 creates 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 can alter the neural circuits that process pain, easing the agony.

In a separate experiment, the researchers at University College showed the brain is a mirror of suffering, reflecting through many of the same neural circuits the pain that others feel, much as if the sensation was its own genuine torment.

Indeed, the brain’s ability to share another’s response to pain at such a fundamental cellular level might 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 mold 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,” said UCLA psychologist Matthew Lieberman. “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 are to be 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 London 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 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 are 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 the patients’ faith in the substance they were given eased their symptoms and also produced physical changes in areas of the brain that process pain.

The greater the brain changes, the greater the reduction in pain, the researchers determined.

At the University of Michigan and Princeton, researchers produced even more compelling evidence that the expectation of relief causes physical changes in how the brain handles pain.

They tested dozens of volunteers by giving them shocks while monitoring their neural activity in a brain scanner.

Then they gave them all 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 regions of the brain, offering tangible 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 depends not only on the actual sensory signals from nerves the brain receives, but also on someone’s emotional state.