While scientists have known for years that psychedelic drugs can strongly alter perception, the exact brain mechanisms behind these changes are still not well understood.
In a recent study published in Communications Biology, researchers from Hong Kong, Singapore, and Germany used high-resolution brain imaging to show that psychedelics may redirect visual processing toward memory-related regions. These new findings could potentially help explain the neural basis of hallucinations.
Vision Becomes Memory
Psychedelic substances mainly target serotonin 2A receptors, which are one of at least 14 types of serotonin receptors in the brain. Earlier research suggests that activating serotonin 2A receptors suppresses normal visual processing, making external information less clear to conscious awareness.
“We have observed in earlier studies that visual processes in the brain are suppressed by this receptor,” said first author Callum White. “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.”
In other words, when sensory input drops, the brain draws on stored memories to fill in the gaps.
Oscillations Influence Perception
In this study, the researchers looked at how psychedelics change communication between brain regions in mice. They found that the drugs increased rhythmic neural activity, called oscillations, in the visual areas of the brain.
Oscillations are waves of brain activity that help different regions communicate. After researchers administered psychedelics, the mice’s visual brain areas produced increasingly strong low-frequency waves at about 5 hertz. These waves activated the retrosplenial cortex, a part of the brain that helps integrate stored information and contextual information from memory.
This shift changed how the brain processed perception. Rather than prioritizing incoming visual signals, the brain entered a state where content from internal memory had a stronger influence.
“The brain thus switches to a new mode in which access to ongoing events is hindered and instead perceptions are increasingly generated from memory contents, a bit like partial dreaming,” said study leader Professor Dirk Jancke.
This partial dreaming state may help explain why psychedelic experiences often combine vivid images with fragments of personal memory.
Imaging the Brain in Real Time
The team used an optical imaging method that records brain activity in real time to study these changes. Researchers genetically modified the mice to produce fluorescent proteins in select brain cells, which let them monitor neural activity in real time.
“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,” Jancke said.
These pyramidal cells create important communication pathways across the cortex. By visualizing their activity, the researchers could see how psychedelic-induced oscillations changed coordination across brain networks.
Implications for Therapy
These findings emphasize why psychedelics are being studied as possible treatments for anxiety, depression, and other psychiatric conditions under medical supervision.
“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,” Jancke said. “It will be exciting to see how such therapies are further personalized in the future.”
By increasing the influence of memory networks on perception, psychedelics may offer a way to revisit and possibly change established thought patterns.
However, the team conducted the study in mice, not humans. Although humans and animals share many neural circuits, researchers cannot directly assess subjective experiences such as hallucinations in animal models. The researchers inferred changes in perception from patterns of brain activity rather than from reported experiences.
Even so, this research provides new insight into how psychedelics change large-scale brain communication. As research on medically supervised psychedelic therapy continues, understanding how these substances change brain networks will become increasingly important. Mapping these altered states in detail may help guide safer and more effective clinical use of psychedelics in the future.
Austin Burgess is a writer and researcher with a background in sales, marketing, and data analytics. He holds a Master of Business Administration, a Bachelor of Science in Business Administration, and a Data Analytics certification. His work combines analytical training with a focus on emerging science, aerospace, and astronomical research.