Despite the rich history and cultural significance of entheogenic substances, the neuroscientific studies bridging psychedelic effects on the brain with the vivid and often mystical experiences persons undergo have only recently begun to take shape. Today, substantial psychedelic research exists, and science has moved beyond simply saying that psychedelics produce altered states of consciousness. Science seeks to understand how.
Hallucinogens or psychedelics are sub-categories of a wider class of drugs called psychoactive substances – substances that interact with the central nervous system to alter mood, cognition, perception, and behavior. When taken, psychedelics cause the brain to reroute its functioning through a dazzling and complex dance of neurochemistry. This complex neurochemistry of psychedelics has been the subject of numerous studies.
At the heart of the psychedelic experience lies the brain’s serotonin system. Serotonin receptors, especially the 5-HT2A receptor, are believed to be primarily responsible for the mind-altering effects of many psychedelics, from LSD to magic mushrooms. These substances seem to mimic the serotonin neurotransmitter, which leads to intensified and altered signalling in the brain.
Officially, most psychedelics fall into one of two classes: the classic hallucinogens, like LSD and psilocybin, and the dissociative drugs, like ketamine and PCP. Yet, in spite of their categorical differences, these substances collectively lead to distinct, recurring features in human experiences, which researchers have labeled as “mystical experiences”. The definition derives largely from the work of pioneering researcher Walter Pahnke, who described phenomena such as a profound sense of unity, a sense of sacredness, peace and joy, and the feeling of transcending time and space. Pahnke also underscored the paradoxical quality of these experiences, or their seeming inability to be adequately captured in language, as one of their hallmarks.
Today, these descriptions form the backbone of the neural correlates of mystical experiences. It is perhaps not surprising, then, that numerous studies have found these substances to have a profound impact on the brain’s normal functioning. Brain imaging and psychedelics further illuminate this complex relationship. Utilizing imaging technologies like functional Magnetic Resonance Imaging (fMRI), researchers have been able to view changes in brain activity patterns in real-time during a psychedelic trip.
One of the most striking findings from such studies is the so-called “ego dissolution” experience. This phenomenon is described as a losing of the sense of self, and the melding of the self and world into one continuous, interconnected entity. Fascinatingly, this experience is often associated with decreased activity in the brain’s default mode network (DMN), a network of brain regions typically more active at rest and linked to self-related thoughts and introspection.
A 2017 study by Leor Roseman, a researcher at Imperial College London, took psychedelic research a step further. He showed that the magnitude of ego dissolution a person experiences during a trip correlates with the degree of visual cortex disintegration. While this doesn’t explain why the phenomenon occurs, the insight brings us closer to learning how psychedelics override the systems within our brains that keep our perception of reality neatly boxed in and our sense of self tactile.
Undoubtedly, there are still many unanswered questions regarding the science behind psychedelic experiences. However, the ground being treaded is not just new: it is immensely fertile. As we delve deeper into understanding the neurobiology of hallucinogens, we open up new frontiers for medicine, psychology, and our understanding of consciousness itself. From treatment for various mental disorders to improving creativity and problem-solving, the potential applications of these substances make them both scientifically enticing and clinically pragmatic.