fMRI proves conquering pain can be mind over gray matter
The expectation of pain relief is enough to induce changes in the brain?s pain pathways, according to a pair of studies by researchers at the Ann Arbor Veterans Affairs Health Care System. Both studies appeared in the February issue of Science.
In the first study, researchers used fMRI to scan 24 subjects while they received both painful and nonpainful shocks to their arms. Subjects reported their experience of pain on a 10-point scale.
Investigators then informed the subjects that they were involved in a study testing antipain creams. Participants received the placebo, got shocked again, and reported their pain experience.
Functional scans after the placebo showed reduced activity in the pain-sensing areas of the brain including the thalamus, somatosensory cortex, and other parts of the cortex.
For the second study, researchers scanned 50 subjects to determine exactly when the patients began to feel the placebo pain-reducing effects. The authors postulated that an earlier reduction of pain would indicate that anticipation of pain relief was the prime motivator for changes in the brain.
Imaging showed that increased activity in the prefrontal cortex during the expectation of relief triggered the subsequent reduction of activity in the brain?s pain-sensing areas fin subjects receiving the placebo.
The prefrontal cortex is involved in several key processes, according to lead author Tor D. Wager, Ph.D., now an assistant professor of psychology at Columbia University. The dorsolateral region most likely maintains expectancy, which may be an ingredient of belief. The orbitofrontal region links environmental cues to motivations and rewards.
?The placebo could elicit an ?I?m safe? kind of response to the warning cue, which could in turn reduce anxiety and/or reduce pain through other mechanisms,? Wager said.
He listed several questions that still need answers: · When and how do placebos affect our behavior? · Do they affect early pain experience or later evaluation of pain? · Is there a type of person who is most likely to respond to placebo and why? · If one shows placebo effects in one setting, is one likely to show them in other settings?
?These results are just a few pieces in our understanding of the larger picture of how beliefs, desires, and expectations affect our experience,? he said.
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