Comparing neural correlates of consciousness: from psychedelics to hypnosis and meditation

Background Pharmacological and non-pharmacological methods of inducing altered states of consciousness (ASC) are becoming increasingly relevant in the treatment of psychiatric disorders. While comparisons between them are often drawn, to date no study has directly compared their neural correlates.Methods To address this knowledge gap we directly compared two pharmacological methods: psilocybin (n=23, dose=0.2mg/kg p.o.) and LSD (n=25, dose=100μg p.o.) and two non-pharmacological methods: hypnosis (n=30) and meditation (n=29) using resting state functional connectivity magnetic resonance imaging (rs-fcMRI), and assessed the predictive value of the data using a machine learning approach.Results We found that (i) no network reaches significance in all four ASC methods; (ii) pharmacological and non-pharmacological interventions of inducing ASC show distinct connectivity patterns that are predictive at the individual level; (iii) hypnosis and meditation show differences in functional connectivity when compared directly, and also drive distinct differences when jointly compared to the pharmacological ASC interventions; (iv) psilocybin and LSD show no differences in functional connectivity when directly compared to each other, but do show distinct behavioral-neural relationships.Conclusion Overall, these results extend our understanding of the mechanisms of action of ASC and highlight the importance of exploring how these effects can be leveraged in the treatment of psychiatric disorders.