Overview
Ego dissolution, the acute loosening of self-world boundaries, predicts clinical benefit in psychedelic therapy. But its neural basis is usually described with global connectivity summaries that are hard to interpret and vulnerable to expectancy and physiological confounds. We propose a concrete alternative: distributed body maps in the brain that anchor the self-other boundary. Our lab recently discovered vicarious body maps, somatotopically organized representations beyond classical somatosensory cortex that respond both to felt touch and to the sight of others' bodies, a shared neural code for self and other. This project tests whether two routes to expanded experience, acute psilocybin and contemplative body-scan training, act on this architecture. Forty psilocybin-experienced, meditation-naive adults complete an intake 7T fMRI session, six weeks of randomized training (daily body-scan practice vs. an active-control attention game), and two double-blind post-training sessions (psilocybin 10 mg vs. placebo, counterbalanced). Each session uses matched tri-modal mapping paradigms xogenous tactile, endogenous attentional, vicarious visual) analyzed with population receptive field models, voxelwise HRF diagnostics, and split-half noise ceilings, so that inference does not depend on unverifiable belief states.
We predict that psilocybin reduces map stability and increases cross-modal coupling in parallel with ego dissolution (H1); that training increases endogenous controllability and reliability of the same maps (H2); and, as the primary test, that training modulates the psilocybin perturbation signature (Group × Drug; H3). Neural changes are aggregated into a preregistered Perception Box Expansion Index (PBEI) and linked to a multimethod experiential composite (PB-X: ego dissolution, interoceptive awareness, boundary malleability, psychological flexibility). Mediation models test whether PBEI changes explain experiential effects. Deliverables include open data, code, and a reusable target-engagement biomarker whose behavioral components are portable to adolescent and community settings.