Psychedelics appear to reshape how the brain builds reality by dampening incoming visual signals and boosting internal memory networks.
Psychedelic compounds act on the brain by binding to serotonin receptors. Scientists have identified at least 14 different receptors that respond to the neurotransmitter serotonin. Among them, psychedelics most strongly target the 2A receptor. This receptor plays several roles, including reducing activity in visual regions of the brain and influencing learning.
“We have observed in earlier studies that visual processes in the brain are suppressed by this receptor,” says Callum White, first author of the study. “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 outside visual input becomes weaker, the brain compensates. Instead of relying fully on incoming signals, it pulls pieces from stored experiences. Those memory fragments blend into perception, producing hallucinations.
Slow Brain Waves Link Vision and Memory
The researchers also examined how this shift unfolds inside the brain. Psychedelics boost rhythmic patterns of neural activity known as oscillations in visual areas. Oscillations are synchronized waves of activity that help different parts of the brain exchange information.
After psychedelics were administered, visual regions began generating stronger low-frequency (5-Hz) waves. These slower waves stimulated another area called the retrosplenial cortex, a key hub involved in accessing stored information. As communication between these regions increases, the brain moves into a different functional state. Awareness of real-time events declines, and perception depends more heavily on memory. As Professor Dirk Jancke, who led the study, explains, the result feels “a bit like partial dreaming.”
Real-Time Imaging of Brain Activity
To observe these changes directly, the team used an optical imaging technique that captures neural activity across the entire surface of the brain in real-time. The experiments relied on specially engineered mice created by Professor Thomas Knöpfel from Hong Kong Baptist University. These mice were genetically modified to produce fluorescent proteins in specific types of brain cells.
This design allowed researchers to trace exactly which cells were active. “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,” says Jancke. These pyramidal cells are essential for transmitting signals both locally and across distant parts of the cortex.
Implications for Depression and Anxiety Treatment
The findings also strengthen the scientific basis for psychedelic-assisted therapy. Psychologists are exploring the use of these substances to help treat conditions such as anxiety disorders and depression.
“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,” says Jancke.
By clarifying how psychedelics reduce external sensory dominance and enhance memory-driven perception, the study sheds light on both the biology of hallucinations and the growing interest in these compounds as therapeutic tools.
Reference: “Psychedelic 5-HT2A agonist increases spontaneous and evoked 5-Hz oscillations in visual and retrosplenial cortex” by Callum M. White, Zohre Azimi, Robert Staadt, Chenchen Song, Thomas Knöpfel and Dirk Jancke, 12 January 2026, Communications Biology.
DOI: 10.1038/s42003-025-09492-9
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