Navigating the chaos of psychedelic fMRI brain-entropy via multi-metric evaluations of acute psilocybin effects
medRxiv – July 03, 2023
Source: medRxiv/bioRxiv/arXiv
Summary
Psychedelics like psilocybin may enhance brain activity in unique ways. In a study with 28 participants, researchers analyzed fMRI scans before and after psilocybin use, revealing significant links between brain entropy and subjective experiences. This nuanced effect suggests certain metrics could be key in understanding psychedelics' clinical benefits.
Abstract
A prominent theory of psychedelics is that they increase brain entropy. Twelve studies have evaluated psychedelic effects on fMRI brain entropy quantifications, no findings have been replicated. Here we evaluated these metrics in an independent 28-participant healthy cohort with 121 pre- and post-psilocybin fMRI scans. We assessed relations between brain entropy and plasma psilocin, brain serotonin 2A receptor occupancy, and a subjective drug intensity rating using linear mixed-effects models. We observed significant positive associations for Shannon entropy of path-length, instantaneous correlation distributions, and divergent associations of sample entropy at varying time-scales. We did not observe significant effects for 8 of 13 entropy metrics. Brain entropy quantifications showed limited inter-measure correlations. Our observations support a nuanced acute psychedelic effect on brain entropy, underscoring the need for replication and that these metrics do not reflect a singular construct. Our findings highlight candidate brain entropy metrics that may mediate clinical effects of psychedelics.