How a person’s brain functions when they are hypnotized to reduce pain is still a mystery. In my research project in psychology at Université de Montréal, I am using algorithms that analyze cerebral activity to ascertain whether the brains of participant subjects are activated synchronously, and determine whether hypnosis alleviates pain in a similar or a unique manner across individuals.

Pain is an unpleasant experience that can be hugely detrimental to quality of life. According to Statistics Canada, more than one million Quebecers (16% of the population) live with persistent pain. In a recent paper in the journal Cerebrum, “Managing Pain,” Tor Wager—one of the most influential international researchers studying pain and the brain—writes that pain is the number one reason why people seek medical attention, and that it affects more people than diabetes, heart disease and cancer combined. There are many efficacious pain-treatment drugs, but they act only over the short term, they are expensive, and using them carries a high risk of dependency.

Indeed, there is currently an opioid crisis in North America linked to increased prescription of painkillers. Unprecedented efforts are under way worldwide to find effective alternative pain management approaches. The International Association for the Study of Pain recently reported that hypnosis has proven effective for reducing pain, and that efforts should be made to incorporate it into current care approaches.

Hypnotists who entertain onstage are certainly fascinating to audiences, but what I find even more intriguing is that hypnosis can be used to alleviate pain—and even eliminate it in some cases. But what is hypnosis, exactly? Hypnosis is a condition of focused attention, accompanied by a heightened capacity to follow suggestions. Verbal suggestions (e.g., “you feel your hand is becoming heavy”) are the key aspects of hypnosis used to target and even modify the experience of pain.

The person undergoing hypnosis to reduce pain is first brought to a state of relaxation and favourable mental disposition. Then they are invited, by means of suggestions, to reinterpret sensations that might normally be painful into tolerable ones. For example, with a patient undergoing arm surgery, the hypnotherapist might have them think of a pleasant environment and imagine themselves in that place. If the patient visualizes themselves on a beach, the hypnotherapist could then suggest that the sensations perceived on their arm are merely windblown grains of sand pinching their skin. Ultimately, pain sensation is reinterpreted according to the mental context induced by the suggestions.

In response to pain stimuli, specific brain regions are activated, resulting in the unpleasant experience of pain. The more intense the stimuli, the more strongly the “cerebral pain network” is activated. One of the intriguing findings with hypnosis is that it reduces cerebral activity in that network when pain is sensed. Hypnotherapy therefore not only reduces perceived pain as reported by subjects; it also reduces the brain activity triggered by pain stimuli. Hypnosis therefore acts on the cerebral pain regions, which in turn influences the person’s subjective experience of pain.

But what is happening in the brain before the pain is reduced by this method? In other words, how does hypnosis prepare the brain so that when painful sensations occur, the brain’s reaction and the experience of perceived pain are attenuated? By measuring cerebral activity during the pain-reduction suggestions, we can study changes in that activity in response to hypnosis, before the pain stimulus occurs.

My project uses measurements of cerebral activity taken by means of functional magnetic resonance imaging (fMRI). While participants are under hypnosis in the MRI machine, they listen to pain-reduction suggestions, and are then exposed to pain stimuli. Analysis algorithms are then used to measure whether the brains of two people are activated synchronously as they listen to the suggestions. For each sample pair, the algorithms calculate whether, in both subjects, the same brain region exhibits a signal that co-varies in a similar manner. This will help determine whether hypnosis engages one or more common mechanisms in the brains of all the hypnotized individuals studied. For example, if activity in one brain region co-varies consistently in all participants when hearing the suggestions, I can conclude that this region plays a significant role in processing the pain-reduction suggestions. My project findings will also be useful for better understanding how the brain interprets and transforms the verbal content of the pain-reduction suggestions.

Hypnosis is an effective tool for reducing both pain-related cerebral activity and the subjective experience of pain, in the brain and in subjective experience, and I am striving to understand the underlying cerebral dynamics. The use of tools derived from artificial intelligence is crucial to gaining a better understanding of this complex phenomenon.