New brain training study could help explain the placebo effect

According to a new study published Monday in Natural medicine. These results could help explain the so-called placebo effect.

The researchers trained 34 participants using a technique called neurofeedback. Just as a person can be trained to lower their heart rate by watching a real-time heart monitor, people can learn to activate parts of their brain by lying in a brain scanner. “We’re opening a kind of window into unconscious neuronal activity,” says Nitzan Lubianiker, co-senior author of the study and a neuroscientist at Yale University.

Participants were encouraged to try different mental strategies, such as thinking about a positive memory or focusing on their body. And using real-time feedback, they learned to activate reward pathways in two deep brain structures called the ventral tegmental area (VTA) and nucleus accumbens.

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Two other groups of participants were trained to activate different brain regions or received no training at all. All participants then received the hepatitis B vaccine. The researchers measured their immune system’s response to the injection by checking the levels of hepatitis B antibodies in their blood two and four weeks later.

People who had higher activity levels in their VTA had higher levels of antibodies in their blood. This suggests that the body mounted a stronger immune response when the VTA reward pathways were activated. The study “is one of the first to show that activity in a specific region of the human brain can be correlated with downstream antibody responses,” says Isaac Chiu, an immunologist at Harvard University, who was not involved in the research.

That said, there were no significant differences in antibody levels between the group that received neurofeedback training focused on reward regions of the brain and the groups that did not. This may be because the nucleus accumbens, the other reward region that some participants were taught to develop, did not have the same connection to the immune response, confusing the results.

Participants who focused on positive expectations during the brain scan were more able to increase their activity in the VTA, while focusing more broadly on happiness or pleasure did not have the same effect.

The result could indicate a potential link to the placebo effect, a phenomenon whereby a simulated intervention yields positive results in people who expect the treatment to benefit them.

“There must be some kind of biological mechanism that explains how, when we expect something positive to happen, something changes in our body,” says Lubianiker. And while this study didn’t explicitly test the placebo effect, it suggests that our minds are connected to our immune systems.

“This result showed the power of positivity. They used very modern and comprehensive methods, but the result is very simple,” says Kyungdeok Kim of Washington University in St. Louis, who was not involved in the study but co-wrote a paper on the results.

Researchers are still working to understand how the connection between the brain’s reward system and the immune system works. Are brain signals transmitted to immune cells in the rest of the body via nerves, Chiu’s wonders, or some other mechanism?

It’s possible that this link has deep evolutionary origins, hypothesizes Tamar Koren, a neuroimmunologist at Sourasky Medical Center in Tel Aviv and co-senior author of the study. Reward signals may have evolved to encourage us to search for food and mate, two activities that can expose us to dangerous pathogens. It makes sense that when we experience a sense of reward, “we’re also boosting our immune response against something that’s potentially harmful to us,” she says.

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