Shamans often listen to rhythmic drumming to induce trance states. Using fMRI, we examined the brain networks associated with trance. Experienced shamanic practitioners listened to rhythmic drumming and entered a trance state or remained in a non-trance state. Trance was associated with stronger network hubs (i.e., greater centrality) in the posterior cingulate cortex (PCC), anterior cingulate cortex (ACC), and left insula/operculum. The PCC region (a “default network” hub involved in internally oriented states) was coactive with ACC and insula (key “salience network” regions involved in amplifying relevant neural streams). This coactivation suggests that an internally oriented neural stream is amplified by the salience network during trance. Additionally, during trance the brain stem and auditory cortex were less connected, suggesting perceptual decoupling (i.e., suppression of the repetitive drumming). In sum, coactive default and salience networks and perceptual decoupling could promote an extended internal train of thought for integration and insight.
