The results of a new study demonstrate that a specific region of the brain is behind the placebo effect. The placebo effect is the result of a patient’s conviction that their treatment will be effective, which actually seems to increase its efficacy, regardless of it being an actual treatment or a placebo.
Researchers from the University of Michigan, in the United States, published the results of a study on the nucleus accubens (NAC) in the neuroscience journal Neuron. The nucleus accubens is the specific region of the brain that plays a role in the phenomenon of reward expectation, that is to say when a person is in a situation where he or she expects a positive outcome.
In this study, researchers explained to the participants that they were testing a new pain-relief drug, and that he or she would receive either the study drug or a placebo. In fact, all volunteers received the placebo. Researchers then proceeded to inject a saline solution in the jaw muscle of the volunteers to cause moderate pain.
They asked the volunteers to evaluate their expectation of the pain-killing effect of the “study drug”, and to indicate the level of relief attained with and without the “study drug”, following the injection to their jaw muscle.
The study was twofold. In the first experiment, researchers measured the release of dopamine from the nucleus accubens. Dopamine is a neurotransmitter that is released by the brain in situations where one expects a “reward”.
Researchers noted that the greater the volunteers had indicated they expected the “study drug” to be effective, the greater the dopamine release from the nucleus accubens. Furthermore, among the participants who had indicated greater pain relief from the “study drug”, researchers observed that the nucleus accubens was more active in those who had received the “study drug” before being injected with the pain-causing agent.
In the second experiment, researchers scanned the volunteers’ brains with magnetic resonance imaging (MRI), while telling them they were to receive various monetary rewards. Researchers noted that the volunteers whose nucleus accubens was more active at the idea of receiving money were those who, in the first experiment, had demonstrated the greatest hope that the pain-relief treatment would be effective.
According to these American researchers, their study demonstrates that the nucleus accubens must indeed be activated for the placebo effect to occur. They hope this information can be used in the development of future treatments for various medical conditions.
Is it all in our heads? Perhaps more than we previously thought…