Brain Connectivity Changes in Meditators and Novices during Yoga Nidra: A Novel fMRI Study

Abstract

Yoga Nidra practice aims to induce a deeply relaxed state akin to sleep while maintaining heightened awareness. Despite the growing interest in its clinical applications, a comprehensive understanding of the underlying neural correlates of the practice of Yoga Nidra (YN) remains largely unexplored. In this novel fMRI investigation, we aim to discover the differences between wakeful resting states and states attained during YN practice. The study included individuals experienced in meditation and/or yogic practices, referred to as meditators (n=30), and novice controls (n=31). The GLM analysis, based on audio instructions, demonstrated activation related to auditory cues without concurrent Default Mode Network (DMN) deactivation. Additionally, meditators exhibited heightened bilateral thalamic activation compared to novices. DMN seed based Functional connectivity (FC) analysis revealed significant reductions in connectivity among meditators during YN as compared to controls. We did not find differences between the two groups during the pre and post resting state scans. Moreover, when DMN-FC was compared between the YN state and resting state, meditators showed distinct decoupling, whereas controls showed increased DMN-FC. Finally, meditators exhibit a remarkable correlation between reduced DMN connectivity during Yoga Nidra and self-reported hours of cumulative meditation and yoga practice. Together, these results suggest a unique neural modulation of the DMN in meditators during Yoga Nidra which results in being restful yet aware, aligned with their subjective experience of the practice. The study deepens our understanding of the neural mechanisms of Yoga Nidra, revealing distinct DMN connectivity decoupling in meditators and its relationship with meditation and yoga experience. These findings have interdisciplinary implications for neuroscience, psychology, and yogic disciplines.