Our brain is amazing, so much so that it is not only capable of creating the lies that we sometimes tell without blushing, but, even more surprising, of lying to ourselves without our noticing. All of this has led to the spread of myths that many of us believe. And then there’s the placebo effect. The word placebo, of Latin origin, is the first person of the future of the verb placere, which means to please. The placebo effect is a phenomenon that tries to explain why some patients improve when given a harmless substance in medical terms. And the question is, how do we know that this is so?
According to recent studies carried out by Jon Kar Zubieta, a Spanish neuroscientist at the University of Michigan, believing that we are taking a medicine activates a region of the brain that is associated with reward and addictions. This region, known as the nucleus accumbens, secretes dopamine when activated (dopamine is a hormone and neurotransmitter involved in other rewarding activities, such as eating or having sex). In this case dopamine also works to relieve pain. Zubieta’s team discovered that the placebo response depends on the activity of this brain region… But how did they do it? Experts at the University of Michigan enlisted a group of volunteers who injected a harmless saline solution into their jaws with the aim of causing pain. The “patients” were then divided into two groups: one received a placebo, while the other group was told they would be given a pain reliever, although they would also be given a placebo.
The next step in the study, published in the journal Neuron, was to scan the volunteers’ brains. It was then that it was discovered that the volunteers in the second group, those who believed to have received an analgesic, showed increased activity in the nucleus accumbens. But the study consisted of a second part. In this case, the participants were part of a game of chance in which they could win some money. The objective was to verify whether dopamine, involved in the mechanism of addiction, is also involved in the placebo effect, regulating the feeling of reward. This part of the investigation was performed using FMRI functional magnetic resonance imaging.
The images followed the volunteers’ activity while playing and found that the same brain region, the nucleus accumbens, was activated when they learned whether they had won or lost the bet. To the surprise of the researchers, those who recorded the most activity during the game were also the ones who responded best to the placebo in the first phase of the experiment. This result is what led researchers to first link the nucleus accumbens and dopamine secretion with the placebo effect and, secondly, to discover that a person’s degree of response to a placebo treatment is profoundly related to the activity that registers the area of the brain destined to anticipate a benefit or a reward.