Psychedelics Relax Priors and Reshape Orbitofrontal Dynamics

Psychedelics like psilocybin and ketamine slow decision times and improve accuracy in mice performing a perceptual task. Behavioral modeling showed these changes stem from increased decision thresholds and a shift toward sensory-driven cognitive states. Whole-brain mapping revealed psychedelics selectively modulate a distributed decision-making network. Calcium imaging in the orbitofrontal cortex showed preserved decision-related selectivity but reduced neuronal correlations, indicating weakened top-down influence and relaxed prior expectations. These circuit-level findings support the REBUS model, suggesting psychedelics reconfigure brain dynamics to promote more deliberate, flexible, and sensory-driven decision policies.

Study at a glance

Abstract

Psychedelics such as psilocybin and ketamine are gaining attention as rapid-acting treatments for psychiatric disorders, yet the mechanisms by which they alter cognition remain unclear. A key hypothesis—the REBUS model—proposes that psychedelics relax high-level priors, allowing bottom-up sensory information to exert greater influence over perception and behavior. Here, we test this model in mice performing a free-response perceptual decision-making task that disambiguates prior-driven and sensory-driven decision strategies. Acute administration of psilocybin or ketamine significantly slowed decision times and improved accuracy. Behavioral modeling that combined drift diffusion and GLM-HMM frameworks revealed that these changes were mediated by increased decision thresholds and a marked shift into sensory-engaged cognitive states. Whole-brain c-Fos mapping identified a distributed decision-making network, with psychedelics selectively modulating cortical and subcortical nodes. Calcium imaging in the orbitofrontal cortex (OFC)—a key region for integrating priors and sensory inputs—revealed preserved decision-related selectivity under psychedelics, while exhibiting reduced neuronal correlations—population-level signatures of weakened top-down influence and relaxed priors. Together, these results provide circuit-level support for the REBUS model, showing that psychedelics reconfigure brain-wide and local dynamics to promote more deliberate, flexible, and sensory-driven decision policies.