Serotonergic psychedelics such as LSD, psilocybin, and DMT alter consciousness and may help treat depression and addiction, but their mechanisms remain unclear. A systematic review and meta-analysis across three levels—subjective experience, neuroimaging, and molecular pharmacology—reveals that medium and high doses of LSD produce stronger visionary restructuring than psilocybin. Neuroimaging shows psychedelics generally strengthen connectivity between brain networks while weakening connectivity within networks. Pharmacologically, LSD triggers more inositol phosphate formation at the 5-HT2A receptor than DMT or psilocin, but no significant differences exist in receptor selectivity among the drugs. The analysis finds high heterogeneity and risk of bias, calling for standardized methods and more research.
Consciousness can be understood not as a single unified thing but as composed of distinct information-theoretic elements. A new approach called Integrated Information Decomposition (ΦID) shifts from measuring how much integrated information a system has to analyzing its composition. This provides a formal way to determine whether consciousness is an emergent phenomenon based on that composition. Two organisms can have the same amount of integrated information yet differ in its composition. A new measure, ΦR, and the ΦR-ing rate quantify how efficiently an entity uses information for conscious processing. This decomposition identifies qualitatively different 'modes of consciousness,' enabling mapping between phenomenology and information-theoretic structure, starting with selfhood.