National Geographic : 2016 Dec
54 national geographic • december 2016 together,” says Wager, now a professor at the Uni- versity of Colorado Boulder and director of a neu- roscience lab there. “And that’s the recipe.” The recipe of belief and experience is finding its way out of the lab and into clinical practice as well. Christopher Spevak is a pain and addiction doctor at the Walter Reed National Military Med- ical Center in Bethesda, Maryland. Every day he sees active service members and veterans with severe injuries, sometimes just days or weeks af- ter they have left the battlefield. This offers him an opportunity to use expectation and condition- ing to tap into internal opioids to stave off, or at least mitigate, long-term pain. When Spevak first meets patients, he doesn’t ask about their injuries or their medical histories—he has all that on file. Instead he asks them about themselves. He might learn that in childhood a person had a favorite eucalyptus tree outside his house or loved peppermint candies. Eventually, if Spevak prescribes opioid painkill- ers, every time the patient takes one, he also has eucalyptus oil to smell or a peppermint to eat— whatever stimulus Spevak knows will resonate. Over time, just as with Jensen’s quick-flash faces or Wager’s skin cream (or for that matter, Pav- lov’s bell), patients start linking the sensory ex- perience to the drugs. After a while, Spevak cuts down on the drug and just provides the sounds or smells. The patient’s brain can go to an internal pharmacy for the needed drugs. “We have triple amputees, quadruple ampu- tees, who are on no opioids,” Spevak says of his Iraq and Afghanistan veteran patients. “ Yet we have older Vietnam vets who’ve been on high doses of morphine for low back pain for the past 30 years.” tWo YearS ago Leonie Koban, a member of Tor Wager’s lab, spearheaded a novel placebo study. The scientists were well aware of the roles of conditioning and theater in channeling expec- tations. They wanted to test the effect of a third element influencing experiences of pain: other believers. As in many previous tests of the placebo effect, the researchers delivered a burning an emeritus professor at the University of Cali- fornia, San Francisco and one of the authors of the study. Since that experiment, conditioning has been used to study the effects of belief on the release of other drugs produced by the body, including serotonin, dopamine, and some cannabinoids, which can work in a way similar to the psycho- active ingredient in marijuana. But it wasn’t until the early 2000s that scientists could watch how these effects play out in the brain. Tor Wa- ger, then a Ph.D. student at the University of Michigan, put subjects in a brain scanner. He applied cream to both of each subject’s wrists, then strapped on electrodes that could deliver painful shocks or heat. He told the subjects that one of the creams could ameliorate pain, but the creams, in fact, were the same, and neither had any inherent pain-reducing qualities. After sev- eral rounds of conditioning, the subjects learned to feel less pain on the wrist coated with the “pain relieving” cream; on the last run, strong shocks felt no worse than a light pinch. A typical condi- tioned placebo response. The most interesting part was what the brain scans showed. Normal pain sensations begin at an injury and travel in a split second up through the spine to a network of brain areas that recog- nize the sensation as pain. A placebo response travels in the opposite direction, beginning in the brain. An expectation of healing in the prefrontal cortex sends signals to parts of the brain stem, which creates opioids and releases them down to the spinal cord. We don’t imagine we’re not in pain. We self-medicate, literally, by expecting the relief we’ve been conditioned to receive. “The right belief and the right experience work We don’t imagine we’re not in pain. We self-medicate, literally, by expecting the relief we’ve been conditioned to receive.