Slow nasal breathing at 2.5 breaths per minute, as practiced in Pranayama, alters brain activity and induces a non-ordinary state of consciousness, primarily through mechanical stimulation of the olfactory epithelium rather than through vagal nerve stimulation. In 12 experienced meditators, slow nasal breathing produced slowing of EEG delta and theta activity in prefrontal regions, widespread increases in theta and high-beta connectivity, increased phase-amplitude coupling between these bands in prefrontal and posterior Default Mode Network regions, and increased small-worldness of high-beta networks. Participants reported a higher perception of being in a non-ordinary state of consciousness compared to mouth breathing at the same rate or resting state.
Yoga nidra, an ancient meditative practice, induces an altered state of consciousness distinct from sleep. In a preliminary study, six healthy volunteers completed 12 guided sessions during a retreat. EEG recordings showed no sleep markers (K-complexes or spindles) during practice. Compared to a resting baseline, participants reported increased dissociative effects, altered body image, reduced rational thinking, and less volitional thought control. One subject's EEG analysis revealed early increases in alpha, beta, and theta power followed by reductions, with gamma power rising in later stages. These findings suggest yoga nidra produces a unique psychophysiological state, though larger studies are needed.