Psychotic disorders present a challenge for research and clinical practice. Their pathogenesis is poorly understood, symptoms vary widely between patients, and there is a lack of objective biomarkers. Psychosis affects GABAergic neuronal inhibition and glutamatergic excitation via NMDA receptors in many areas of the cerebral cortex. Using magnetoencephalography source imaging, we mapped psychosis-related alterations of several features of intrinsic neural population dynamics across the human cortex. The cortex-wide patterns of changes in neural dynamics in first-episode psychosis patients resembled the corresponding patterns observed in individuals with clinical high-risk for psychosis. In both clinical groups, these cortex-wide patterns of changes in neural dynamics resembled the patterns of the effects of pharmacological manipulations of GABA-A or NMDA receptor functions in healthy participants. Individual differences in the level of pattern similarity to the effects of GABA-A or NMDA receptor manipulations correlated with the strength of patients' positive symptoms or negative symptoms, respectively. Our study opens a new window on the pathophysiology of psychosis.