Brain Network Reconfiguration and Perceptual Decoupling During an Absorptive State of Consciousness.

Trance, an absorptive state with narrowed external awareness used by shamans for insight, was studied with fMRI in 15 experienced shamanic practitioners listening to rhythmic drumming. During trance, three brain regions—posterior cingulate cortex, dorsal anterior cingulate cortex, and left insula/operculum—showed stronger hubs (higher eigenvector centrality). The posterior cingulate cortex, a default network hub for internal thought, coactivated with control-network regions, suggesting amplified internal neural streams. Auditory pathway seeds were less connected, indicating perceptual decoupling from repetitive drumming. This network reconfiguration may support extended internal thought and insight.

Study at a glance

Abstract

Trance is an absorptive state of consciousness characterized by narrowed awareness of external surroundings and has long been used-for example, by shamans-to gain insight. Shamans across cultures often induce trance by listening to rhythmic drumming. Using functional magnetic resonance imaging (fMRI), we examined the brain-network configuration associated with trance. Experienced shamanic practitioners (n = 15) listened to rhythmic drumming, and either entered a trance state or remained in a nontrance state during 8-min scans. We analyzed changes in network connectivity. Trance was associated with higher eigenvector centrality (i.e., stronger hubs) in 3 regions: posterior cingulate cortex (PCC), dorsal anterior cingulate cortex (dACC), and left insula/operculum. Seed-based analysis revealed increased coactivation of the PCC (a default network hub involved in internally oriented cognitive states) with the dACC and insula (control-network regions involved in maintaining relevant neural streams). This coactivation suggests that an internally oriented neural stream was amplified by the modulatory control network. Additionally, during trance, seeds within the auditory pathway were less connected, possibly indicating perceptual decoupling and suppression of the repetitive auditory stimuli. In sum, trance involved coactive default and control networks, and decoupled sensory processing. This network reconfiguration may promote an extended internal train of thought wherein integration and insight can occur.