Tf. Varley

2 papers in the library · 8 citations · publishing 2019

Papers

Serotonergic Psychedelics LSD & Psilocybin Increase the Fractal Dimension of Cortical Brain Activity in Spatial and Temporal Domains

bioRxiv (Cold Spring Harbor Laboratory) January 11, 2019 Tf. Varley, Robin Carhart-Harris, Leor Roseman et al. 8 citations preprint

Psychedelic drugs like LSD and psilocybin increase the fractal dimension of brain activity, indicating a shift toward a critical state between order and chaos. Using fMRI data, researchers measured the fractal dimension of functional connectivity networks and BOLD time-series. Both drugs significantly increased the fractal dimension of functional connectivity networks; LSD also significantly increased the fractal dimension of BOLD signals, while psilocybin showed a non-significant trend in the same direction. Changes localized to the dorsal-attentional network. These findings support the Entropic Brain Hypothesis, which proposes that psychedelics alter consciousness by moving the brain closer to a critical tipping point.

DOI: 10.1101/517847 Full text Psilocybin Serotonergic Serotonin Fractal dimension +11

Fractal Dimension of Cortical Functional Connectivity Networks Predicts Severity in Disorders of Consciousness

bioRxiv Preprint Server October 1, 2019 Tf. Varley, M. Craig, R. Adapa et al. preprint

Brain activity's fractal dimension—a measure of complexity—decreases with loss of consciousness. Healthy volunteers showed higher fractal dimension than patients in a minimally conscious state, who in turn showed higher dimension than those in a vegetative state, regardless of injury cause. Fractal dimension of functional connectivity networks, adjacency matrices, and BOLD time-series all correlated with level of consciousness. These findings support the idea that consciousness requires complex, critically organized brain activity, consistent with prior EEG, MEG, and fMRI work.

DOI: 10.1101/789636 Full text