Brain activity linked to placebo effect increases antibody levels after vaccination
Positive thinking can strengthen the body’s defenses against illness.
Increased activity in a region of the brain that controls motivation and expectations, particularly the brain’s reward system, is linked to produce more antibodies after receiving a vaccine. The results suggest that these increases were linked to the placebo effect, the researchers report January 19 in Natural medicine.
“The placebo is a self-help mechanism, and here we are really exploiting it,” says Talma Hendler, a neuroscientist at Tel Aviv University. “This suggests that we could use the brain to help the body fight disease.”
The work is important because it “is the first human evidence of a relationship between brain reward systems and immune function,” says Tor Wager, a neuroscientist at Dartmouth College in Hanover, New Hampshire, who was not involved in the study. The study was not designed to test the effectiveness of the vaccine. Larger studies, including more comprehensive immune assessments, will be needed to test this association as a medical intervention.
Scientists have discovered many links between the brain and body health. Negative and positive mental states can affect the immune systemand studies in rodents have suggested that the brain’s reward network East involved in these effects.
To find out if the same circuits were at play in humans, Hendler and his colleagues trained healthy volunteers to regulate their brain activity using neurofeedbacka technique that uses brain imaging to show users activity in the area they are trying to stimulate. The team randomly assigned 85 participants to receive training aimed at increasing activity either in their rewards network or another network, or to receive no training at all.
Immediately after the final training session, participants received a hepatitis B vaccine. Researchers measured antibody levels in the volunteers’ blood before vaccination and then twice afterward. Comparing each participant’s brain activity with changes in their antibody levels showed that those who maintained higher activation in the ventral tegmental area (VTA) of the reward network during training produced more antibodies in response to the vaccine.
The team then identified the factors that led to higher VTA activation. Participants were more successful in stimulating their VTA activity when their mental strategy included positive expectations, rather than other mental content, such as visual images. The researchers link this result to the placebo effectwhich occurs when a person feels better after a fake treatment that they expect to work.
The study could not discern any difference in the immune response between the reward network group and either of the other two groups. Looking back, it’s not surprising that the two types of brain training showed no difference, says Nitzan Lubianiker, a neuroscientist at Yale University. The reward network training did not focus exclusively on the VTA because he and his colleagues did not know in advance how to target it. Additionally, “neurofeedback is itself a rewarding task,” says Lubianiker, because participants receive visual feedback showing when they are doing well. Brain scans showed that both types of training activated the VTA.
In other words, “the immune effect appears to scale to how effectively individuals engage specific brain circuits, not just an experimental condition,” says Jonathan Kipnis, an immunologist at Washington University School of Medicine in St. Louis, who was not involved in the study but wrote a paper. accompanying commentary article.
The team is conducting animal studies to trace the VTA’s connections to other regions of the brain, to better understand how the brain might influence the immune system.
Future studies could use neurofeedback that specifically targets the VTA, and a control condition that avoids activating it, to clarify the utility of neurofeedback in driving immune responses, says Michael Irwin, a psychoneuroimmunologist at the University of California, Los Angeles, who was not involved in the work.
The result should motivate researchers to replicate it in larger studies, Wager says. “If these results are confirmed, it could change the way we think about how to provide effective vaccination. »
