The psychedelic state involves a breakdown in patterns of information flow in the brain. Using MEG recordings, researchers measured functional connectivity after administration of LSD, psilocybin, and low-dose ketamine, and compared them with the non-psychedelic drug tiagabine. All three psychedelics decreased directed functional connectivity (information flow) throughout the brain, as measured by Granger causality. For LSD, this decrease was coupled with an increase in undirected functional connectivity (correlation and coherence), a surprising opposite movement that highlights the importance of comparing multiple measures of functional connectivity in neuroimaging data.
Lysergic acid diethylamide (LSD) alters how the brain processes unexpected sounds by modulating effective connectivity and neural adaptation mechanisms. In an auditory oddball paradigm, LSD changes communication pathways between brain regions involved in sensory processing, affecting how the brain responds to and adapts to novel or deviant auditory stimuli. These findings suggest that psychedelics can fundamentally reshape brain network dynamics underlying auditory perception.