Researchers have discovered that psychedelic substances suppress visual processing in the brain, leading to hallucinations by drawing on memory fragments. The study, conducted using advanced imaging on mice, shows how slow brain waves shift perception toward internal recall. These findings could inform therapies for depression and anxiety.
Psychedelic substances interact with the brain by binding to serotonin receptors, particularly the 2A receptor, which influences learning and reduces activity in visual processing areas. Callum White, the study's first author, explained: "We have observed in earlier studies that visual processes in the brain are suppressed by this receptor. This means that visual information about things happening in the outside world becomes less accessible to our consciousness. To fill this gap in the puzzle, our brain inserts fragments from memory -- it hallucinates."
When external visual signals weaken, the brain compensates by accessing stored images and experiences, blending them into perception to create hallucinations. The research identified that psychedelics boost low-frequency 5-Hz oscillations in visual regions. These waves enhance communication with the retrosplenial cortex, a area key to memory retrieval, altering the brain's mode to prioritize internal information over external stimuli.
Professor Dirk Jancke, who led the study, described the state as "a bit like partial dreaming." To observe this, the team employed optical imaging to monitor neural activity across the mouse brain in real time. The mice, engineered by Professor Thomas Knöpfel at Hong Kong Baptist University, expressed fluorescent proteins in specific cells, allowing precise tracking. Jancke noted: "We therefore know exactly in our experiments that the measured fluorescent signals originate from pyramidal cells of the cortical layers 2/3 and 5, which mediate communication within and between brain regions."
The results suggest potential for psychedelic-assisted therapy under medical supervision, where these substances might help recall positive memories and disrupt negative thought patterns. Jancke added: "When used under medical supervision, such substances can temporarily change the state of the brain to selectively recall positive memory content and restructure learned, excessively negative thought patterns, i.e., to be able to unlearn negative context. It will be exciting to see how such therapies are further personalized in the future."
The study appears in Communications Biology.
