Psychedelics May Quiet Reality While Amplifying Memories, Researchers Find
Psychedelic drugs appear to alter perception by reducing how strongly the brain processes the outside world while increasing the influence of internally stored memories. New research suggests this shift depends on a specific serotonin receptor and slow brain rhythms that redirect neural activity away from sensory input and toward internally generated experiences.
Scientists have long known that psychedelics interact with serotonin receptors, a large family of receptors involved in mood, learning and sensory processing. The new study highlights the important role of the serotonin 2A receptor, which is highly concentrated in the cortex and strongly targeted by classic psychedelics such as LSD and psilocybin.
In visual regions of the brain, activation of the 2A receptor appears to weaken the normal processing of external visual information. Lead author Callum White explains that when this receptor becomes active, sensory signals become less accessible to conscious awareness. As outside information loses influence, the brain increasingly relies on memories and internally generated associations to interpret experience.
Rather than accurately representing the external environment, neural circuits begin blending fragments of past experiences into perception. These internally generated images, emotions and associations mix with reduced sensory input, producing the vivid hallucinations and altered perceptions often reported during psychedelic experiences.
Slow brain waves may shift perception inward
The researchers also tracked how these changes develop moment by moment in the brain. After psychedelics were administered, they observed an increase in low-frequency brain oscillations — slow rhythmic waves around 5 hertz — within visual brain regions.
These slow waves help coordinate communication between distant parts of the brain and can reshape how information flows across the cortex. As the oscillations strengthened, activity also increased in the retrosplenial cortex, a region associated with navigation, scene construction and autobiographical memory.
The stronger connection between visual regions and memory-related brain areas suggested a shift toward a more internally focused mode of perception. In this state, awareness of present external events becomes weaker, while perception depends more heavily on recalled images, emotions and personal narratives.
Study leader Dirk Jancke compared the experience to a partial dream state, where waking reality becomes overlaid with internally generated content drawn from memory and imagination.
The findings align with previous human imaging studies showing that psychedelics disrupt large-scale brain networks responsible for maintaining a stable sense of self and reality. As those networks loosen, sensory regions appear to become more influenced by memory, expectation and imagination.
Imaging psychedelic brain activity in real time
To observe these processes in detail, researchers used wide-field optical imaging to monitor activity across the surface of the mouse brain in real time. This method tracks fluorescent signals linked to activity in specific groups of neurons, allowing scientists to visualize rapid changes in brain communication during psychedelic exposure.
The experiments used genetically engineered mice developed by Thomas Knöpfel at Hong Kong Baptist University. These mice express fluorescent proteins in selected cortical neurons, enabling researchers to observe when and where those cells become active.
Jancke explained that the recorded signals came primarily from pyramidal neurons located in cortical layers 2/3 and 5. These neurons play a central role in communication both within brain regions and across larger cortical networks, making them especially important for understanding how psychedelics alter information flow.
By mapping changes in these neuronal populations, the team connected receptor activation, slow brain rhythms and altered visual processing into a unified model. Their results support the idea that psychedelics reorganize communication across the cortex, temporarily prioritizing internal memory networks over real-time sensory input.
Possible implications for mental health treatment
The findings may also help explain why psychedelic-assisted therapies are being actively studied for conditions such as depression, anxiety, PTSD and addiction.
Many patients undergoing psychedelic therapy describe revisiting painful memories from a new emotional perspective or reconnecting with long-forgotten positive experiences. Jancke and colleagues suggest that psychedelics may temporarily loosen rigid patterns of negative thinking by changing how the brain accesses and recombines memories.
When external sensory input becomes less dominant, the brain may gain greater flexibility to explore and reinterpret past experiences under therapeutic guidance.
Recent clinical studies involving psilocybin and MDMA have reported long-lasting reductions in depressive symptoms and trauma-related distress, often after only one to three carefully supervised sessions combined with psychotherapy. Researchers caution, however, that these treatments require controlled clinical settings, proper screening and professional follow-up.
Understanding how serotonin receptors, brain rhythms and memory circuits interact during psychedelic states may eventually help researchers refine future therapies. Scientists hope this knowledge could improve treatment timing, dosing and psychological support while reducing the risk of confusion or distress.
As psychedelic therapies continue moving through clinical trials and regulatory review, researchers emphasize that these substances are not simple mood enhancers. Instead, they appear to temporarily reorganize how the brain processes reality itself, shifting perception away from external sensory information and toward internally generated experiences rooted in memory and imagination.
