The neurobiological mechanisms behind psychiatric disorders like treatment-resistant major depression, PTSD, and substance use disorders are not well understood. Psychedelic compounds such as psilocybin, LSD, and DMT show promise as therapies, possibly by inducing neuroplasticity and altering brain functional networks, but how these effects occur remains unclear. This review synthesizes current knowledge from fMRI and PET studies on functional brain changes after these psychedelics in humans, aiming to improve diagnostics and treatment for neuropsychiatric illness.
Psilocybin treatment in male mice led to structural connectivity differences in the frontal association cortex after 72 hours and microstructural changes in the primary visual cortex after 24 hours, as well as in the striatum and hippocampus after 72 hours, including increased mean diffusivity and decreased neurite density. These findings suggest that diffusion microstructure imaging can detect and characterize brain changes induced by psilocybin, offering a potential method to monitor treatment response and identify clinical endpoints for patients with major depressive disorder.