Four methods of inducing altered states of consciousness—psilocybin, LSD, hypnosis, and meditation—produce distinct patterns of brain connectivity, not a single shared neural signature. Pharmacological and nonpharmacological interventions showed connectivity patterns that could predict which method a person had used. Hypnosis and meditation differed from each other and from the drugs. Psilocybin and LSD did not differ in brain connectivity but showed different relationships between brain activity and behavior. The findings clarify how each method works in the brain and suggest they may offer different therapeutic avenues for psychiatric disorders.
Hypnosis alters information processing in the brain's frontoparietal regions, particularly by reducing interhemispheric connectivity and the efficiency of information passing through individual cortical nodes. In a study of 30 hypnosis experts, high-density EEG was recorded during two hypnotic states of different depth—Somnambulism (light) and Esdaile (deep)—and two well-matched control states. Interhemispheric frontoparietal connectivity distinguished hypnosis from control conditions, but no difference was found between the two hypnotic states. Theta power was enhanced during hypnosis. The findings support the idea that altered top-down control in frontoparietal regions facilitates hypnosis by integrating information between cortical hemispheres.