You are getting sleepy, very sleepy… Besides these ‘entertaining,' spectacular, and often funny (but equally frightening) aspects, hypnosis is also a real medical approach used to reduce pain or as a cure for phobias. But hypnosis remains an enigma. A study published in the British review Cerebral Cortex is helping to uncover part of the mystery. So what happens in the brain during hypnosis?

For their study, researchers from Stanford first gave a test to 545 students and then selected 57 for further experimentation. Among them, 36 were considered to be easily hypnotizable, while the others (n=21) were considered to be insensitive to hypnosis. According to psychologist and co-author David Spiegel: “In general, people who are hypnotizable tend to be less self-conscious, trust other people more… and use their imaginations more.” The hypnotizable subjects were then guided in two ways: in one procedure, they were asked to imagine a time when they felt happy; and in the other, they were asked to imagine themselves on vacation. In order to study brain activity during hypnosis, the researchers used functional magnetic resonance imaging (fMRI). What did they observe?

When the hypnotizable participants are under hypnosis, the activity of certain brain regions is reduced (particularly that of the dorsal anterior cingulate cortex). These areas usually help up to recognize our surroundings by deciding which areas in our environment we should focus on or ignore. Thus, a person under hypnosis can see in great detail; but they have a harder time seeing their surroundings. So under hypnosis we can focus on one particular task without worrying about the external environment.

The researchers indicated that hypnosis could allow us to better direct our attention and better control inhibition. According to them, the networks associated with communication between the body and spirit are also better connected during a hypnotic state. While the visualization of the effects of hypnosis on the brain deserves to be extended to a larger cohort, this study already suggests that hypnosis could help people to better control their physical reactions to certain thoughts and stress factors.