Perceptual inference—how the brain integrates visual features into a coherent whole—depends on recurrent processing, the back-and-forth communication between higher and lower cortical regions. Animal studies have implicated NMDA receptors in this process, but human evidence was lacking. In two double-blind, placebo-controlled experiments with healthy participants, the NMDA receptor antagonist memantine selectively improved the brain's ability to decode complex visual illusions (Kanizsa triangles) that require recurrent processing, while leaving simpler visual processing (contrast and collinearity) unaffected. This enhancement occurred only when stimuli were attended and consciously perceived. The findings suggest that blocking NMDA receptors can enhance recurrent processing for attended objects, linking animal and human research on the neural basis of conscious perception.
In a small open-label trial, ten women with postpartum depression received up to three escalating doses of inhaled GH001 (a synthetic form of 5-MeO-DMT) on a single day. Depressive symptoms, measured on the Montgomery-Asberg Depression Rating Scale, dropped by an average of 35.4 points from a baseline of 36.7 by day 8, and all participants met criteria for both response and remission. Improvements were first noted two hours after the final dose. The treatment was well tolerated, with only mild to moderate side effects, most commonly headache. These preliminary findings suggest GH001 may produce rapid and substantial antidepressant effects in postpartum depression, but larger controlled trials are needed.
A rigorous investigation of psychedelic experience requires studying both its neurobiological changes and its subjective dimensions, as these two domains are equally important for understanding the full effects of psychedelics.