An interhemispheric frontoparietal network supports hypnotic states

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.

Study at a glance

Abstract

Understanding the neural substrate of altered conscious states is an important cultural, scientific and clinical endeavour. Although hypnosis causes strong shifts in conscious perception and cognition, it remains largely unclear how hypnosis affects information processing in cortical networks. Here we manipulated the depth of hypnotic states to study information processing between cortical regions involved in attention and awareness. We used high-density Electroencephalography (EEG) to record resting-state cortical activity from 30 hypnosis experts during two hypnotic states with different depth. Each participant entered *Somnambulism*, a sleep-walking-like light hypnotic state, and *Esdaile*, a coma-like deep hypnotic state, and two well-matched control states. Bridging top-down and lateralization models of hypnosis, we found that interhemispheric frontoparietal connectivity distinguished hypnosis and control conditions, while no difference was found between the two hypnotic states. Using a graph-theoretic measure, we revealed that the amount of information passing through individual nodes (measured via betweenness centrality) is reduced during hypnosis relative to control states. Finally, we found that theta power was enhanced during hypnosis. Our result contributes to the current discussion around a role for theta power in bringing about hypnotic states, as well as other altered conscious states. Overall, our findings support the notion that altered top-down control in frontoparietal regions facilitates hypnosis by integrating information between cortical hemispheres.