This is an open-label, single-arm, pilot study exploring the neural, sensory, and cognitive effects of a single, medium dose of psilocybin in patients with chronic pain who already have implanted sensing-capable deep brain stimulation (DBS) devices. Outcomes include multi-site neural recording from previously placed ambulatory sensing-capable DBS devices, quantitative sensory and cognitive testing, and self-reports of pain. We hypothesize that psilocybin will change functional connectivity, decrease clinical and task-based pain reports, and improve cognitive functions.