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.