Psilocybin induces fast and sustained improvements in mental well-being, yet its long-term mechanisms are not fully understood. Four weeks after a full dose, fronto-striatal-thalamic (FST) circuitry—involved in goal-directed behavior and motivation—shows increased dynamic activity and flexibility in healthy volunteers. Computational modeling indicates that reduced structural constraints on functional dynamics cause this increased flexibility. Long-term changes include increased bottom-up and reduced top-down information flow, mediated by serotonergic (5-HT2A) and dopaminergic (D2) receptor systems. This functional re-organization of FST circuits may represent a common mechanism underlying clinical improvements across neuropsychiatric disorders such as substance abuse, major depression, and anorexia.
A computational model predicts that a single dose of psilocybin can produce lasting changes in the dynamic activity and effective connectivity of fronto-striatal-thalamic brain circuits. The modeling suggests that psilocybin may strengthen connectivity between the prefrontal cortex and striatum while altering thalamic gating, effects that persist beyond the acute drug experience. These changes could underlie the sustained therapeutic benefits observed in clinical settings, such as reduced depressive symptoms and increased psychological flexibility. The findings provide a mechanistic framework for understanding how psilocybin induces long-term neural plasticity and highlight potential circuit targets for treating psychiatric disorders.