Psychophysiological and phenomenological characterization of altered states of consciousness induced by Nidrâ Yoga sessions in expert practitioners

Traditional teaching and anecdotical reports describe the millenary technique of Nidrâ Yoga as able to induce altered states of consciousness characterized by deep relaxation, strong concentration, acute self-awareness, and joy. In modern Contemplative Neuroscience, no study investigated the integrated psychophysiological and phenomenological effects of Nidrâ Yoga. Six healthy volunteers (4 females, age range: 31-74 yo) expert of Nidrâ Yoga practices (10-12 years) were recorded during a 6-days retreat period at Somapa, a yoga centre in Eyragues (France) under the banner of R.A.S.A. and Nidrâ Yoga International. High-density-EEG, ECG and respirogram were registered before, during, and after a two-hours Nidrâ Yoga group session, guided by an expert master Yogi with decades of worldwide study and teaching experience of Nidrâ tradition. Psychometric data regarding the state of consciousness (Phenomenology of Consciousness Inventory) and dissociative experiences (Clinician Administered Dissociative States Scale) were collected before and after Nidrâ Yoga sessions. Data were analysed using repeated-measures ANOVA. After Nidrâ Yoga (compared to baseline), subjects reported: i) an altered state of consciousness (p<0.01); ii) dissociative-like effects (p<0.001); iii) increased joy (p<0.01); iv) subjective bodily expansion (p<0.001); v) sacred meanings attributed to the experience (p<0.05); vi) reduced rational thinking (p<0.05); and vii) reduced volitional thoughts control (p<0.01). EEG analyses are in progress and preliminary results on two subjects show an increase of theta band power and of cortical functional connectivity. Nidrâ Yoga is a powerful technique for eliciting altered states of consciousness, sustained by specific psychophysiological and phenomenological correlates, and whose therapeutic potential needs further studies.