"Previous studies have indicated that this receptor suppresses visual processes in the brain," explains Callum White, the study's lead author. "As a result, our consciousness has limited access to visual information from the external environment. To bridge this gap, our brain retrieves fragments from memory, leading to hallucinations."
In essence, when visual signals are diminished, the brain compensates by accessing stored images and experiences. These internally generated fragments can merge with perception, resulting in hallucinations.
Slow Brain Waves Influence Memory Perception
The research team also revealed how this transformation occurs in real-time. Psychedelics enhance rhythmic brain activity patterns, known as oscillations, in visual areas. These oscillations are synchronized waves of neural firing that facilitate communication between different brain regions.
Following the administration of psychedelics, the researchers noted an increase in low-frequency (5-Hz) waves in the visual cortex. These slower waves stimulated the retrosplenial cortex, a crucial hub for accessing stored memories. As this communication intensifies, the brain shifts into a different operational state. Awareness of current external events diminishes, while perception increasingly relies on recalled information. As Professor Dirk Jancke, who led the study, describes it, the experience resembles "a bit like partial dreaming."
Real-Time Brain Imaging Unveils Mechanisms
To observe these changes, scientists employed an advanced optical imaging technique that monitors neural activity across the brain's surface in real time. The experiments utilized specially engineered mice developed by Professor Thomas Knöpfel at Hong Kong Baptist University, designed to produce fluorescent proteins in specific brain cell types.
This innovative approach enabled researchers to accurately identify the origin of the recorded signals. "Thus, we can confirm that the fluorescent signals we measured originate from pyramidal cells in cortical layers 2/3 and 5, which facilitate communication within and among brain regions," states Jancke. These cells are vital for transmitting information throughout the cortex.
Potential Implications for Treating Depression and Anxiety
The study's findings may enhance psychedelic-assisted therapy. Researchers suggest that, under medical supervision, these substances can temporarily alter brain activity to promote the recall of positive memories while diminishing deeply rooted negative thought patterns.
"When administered under medical guidance, these substances can selectively shift the brain's state to recall positive memories and restructure excessively negative thought patterns, allowing for the unlearning of negative contexts. It will be fascinating to see how these therapies evolve in the future," remarks Jancke.
By elucidating how psychedelics redirect perception from the external world to internal memory networks, this study offers a clearer biological foundation for both hallucinations and the expanding therapeutic potential of these compounds.
