Using EEG to measure MMN during hypnosis: A preliminary study.

Hypnosis is commonly used to deal with acute and chronic pain, anxiety, or addictions. However, it is difficult to quantify its effectiveness and measure it in real-time. In this preliminary study, we aimed to identify biomarkers using EEG during hypnosis. We developed an experimental protocol based on a covert attentional task, not requiring the participants to answer to any stimuli neither focus on them, but rather to focus and follow the hypnotist suggestions. We were able to identify an evoked related potential (ERP), the mismatch negativity, elicited by the sound played during the experiment. This ERP showed signs of modulation linked to the participant state (hypnosis or control condition) as well as an amplitude linked to the level of hypnotizability. This potential can be measured mostly on central and frontal electrodes, making it a good candidate for a future medical device that could be worn for example during small surgeries. We also find a bandpower index that could inform about the transition from the induction to the hypnosis phase. The final goal would be to develop a medical device that could help the hypnotist with patient training and monitoring.