Psilocybin-assisted mindfulness training modulates self-consciousness and brain default mode network connectivity with lasting effects. Author: Smigielski L1, Scheidegger M2, Kometer M2, Vollenweider FX2 Affiliation: <sup>1</sup>Neuropsychopharmacology and Brain Imaging, Department of Psychiatry, Psychotherapy and Psychosomatics, University Hospital of Psychiatry, University of Zurich, Lenggstrasse 31, 8032, Zurich, Switzerland. Electronic address: lukasz.smigielski@uzh.ch. <sup>2</sup>Neuropsychopharmacology and Brain Imaging, Department of Psychiatry, Psychotherapy and Psychosomatics, University Hospital of Psychiatry, University of Zurich, Lenggstrasse 31, 8032, Zurich, Switzerland. Conference/Journal: Neuroimage. Date published: 2019 Apr 6 Other: Volume ID: 196 , Pages: 207-215 , Special Notes: doi: 10.1016/j.neuroimage.2019.04.009. [Epub ahead of print] , Word Count: 226 Both psychedelics and meditation exert profound modulatory effects on consciousness, perception and cognition, but their combined, possibly synergistic effects on neurobiology are unknown. Accordingly, we conducted a randomized, double-blind, placebo-controlled study with 38 participants following a single administration of the psychedelic psilocybin (315 μg/kg p.o.) during a 5-day mindfulness retreat. Brain dynamics were quantified directly pre- and post-intervention by functional magnetic resonance imaging during the resting state and two meditation forms. The analysis of functional connectivity identified psilocybin-related and mental state-dependent alterations in self-referential processing regions of the default mode network (DMN). Notably, decoupling of medial prefrontal and posterior cingulate cortices, which is thought to mediate sense of self, was associated with the subjective ego dissolution effect during the psilocybin-assisted mindfulness session. The extent of ego dissolution and brain connectivity predicted positive changes in psycho-social functioning of participants 4 months later. Psilocybin, combined with meditation, facilitated neurodynamic modulations in self-referential networks, subserving the process of meditation by acting along the anterior-posterior DMN connection. The study highlights the link between altered self-experience and subsequent behavioral changes. Understanding how interventions facilitate transformative experiences may open novel therapeutic perspectives. Insights into the biology of discrete mental states foster our understanding of non-ordinary forms of human self-consciousness and their concomitant brain substrate. Copyright © 2019 Elsevier Inc. All rights reserved. KEYWORDS: Consciousness; Default mode network; Meditation; Mindfulness; Psychedelic; fMRI PMID: 30965131 DOI: 10.1016/j.neuroimage.2019.04.009