Scientific Reports
April 19, 2017
Michael Schartner, Robin Carhart‐Harris, Adam B. Barrett et al.
450 citations
Measures of neural signal diversity, such as entropy and Lempel-Ziv complexity, are higher during wakeful rest than during anesthesia. In this study, these measures were computed for spontaneous magnetoencephalographic signals from humans under psilocybin, ketamine, and LSD. All three psychedelics produced reliably higher signal diversity, even after controlling for spectral changes, with the most pronounced increase in temporal (single-channel LZ complexity) rather than spatial diversity. Selective correlations emerged between changes in signal diversity and the intensity of psychedelic experience. This is the first time these measures have been applied to the psychedelic state and have yielded values exceeding normal waking consciousness, suggesting that psychedelic phenomenology constitutes an elevated level of consciousness.
bioRxiv (Cold Spring Harbor Laboratory)
November 2, 2020
Pedro A. M. Mediano, Fernando E. Rosas, Christopher Timmermann et al.
39 citations
preprint
Psychedelics reliably increase brain entropy (neural signal diversity), an effect linked to psychological changes and opposite to the decrease seen during loss of consciousness. This study investigated how context—specifically stimulus manipulation—modulates that entropy increase. Participants under LSD or placebo experienced eyes-closed versus eyes-open conditions, or no stimulus, music, or video. Brain entropy rose with LSD across all conditions but was largest with eyes closed. Entropy changes consistently matched subjective ratings of the psychedelic experience, except during video viewing, suggesting competition between external stimuli and internal LSD-induced imagery. The findings provide quantitative evidence that context shapes neural dynamics during psychedelic experiences, supporting the practice of eyes-closed psychedelic psychotherapy, and challenge simplistic views of brain entropy as a direct measure of conscious level.
arXiv Preprint Archive
February 25, 2025
Romy Beauté, David J. Schwartzman, Guillaume Dumas et al.
Stroboscopic light stimulation on closed eyes typically induces simple visual hallucinations—vivid, geometric, and colorful patterns. An analysis of 862 open-ended reports from the Dreamachine immersive experience, using large language models and topic modeling, confirmed these simple hallucinations and also revealed altered states of consciousness and complex hallucinations. This computational approach enables systematic study of subjective experiences beyond standard questionnaires, capturing subtle patterns not readily identified through closed-form questions. The findings broaden understanding of stroboscopically induced phenomena and demonstrate the potential of natural language processing in computational neurophenomenology.
arXiv Preprint Archive
February 12, 2019
Adam B. Barrett, Pedro A. M. Mediano
Integrated Information Theory (IIT) defines consciousness as a fundamental property of physical systems, measured by the quantity Phi. For IIT to be credible, Phi must be uniquely defined and always well-defined. This article identifies three ways in which the current formulation of Phi fails these standards, making the measure ambiguous or ill-defined in certain cases, and discusses potential solutions to address these foundational issues.
arXiv Preprint Archive
July 3, 2014
Adam B. Barrett
Consciousness may arise from information intrinsic to fundamental electromagnetic fields, according to a hypothesis that unites fundamental physics with empirical neuroscience. The proposal extends Integrated Information Theory, which says consciousness comes from intrinsic information generated by dynamical systems, but which existing formulations cannot apply to standard physical models. By treating electromagnetic fields as fundamental, the hypothesis bypasses the need for quantum effects while aligning with known neural correlates of consciousness. This approach aims to eliminate dualistic 'ghosts' by describing consciousness as an aspect of the physical world.