What is the science behind psychedelic visuals? Why do people experience common visual effects with psychoactive substances? And why do people have visuals at all when they embark on psychedelic journeys?
When you journey with psychedelics, you can experience a range of visual effects. These effects can be mild or fully immersive. They can include a stunning display of colors, geometry, symbols, images, scenes, and even storylines. Many psychedelic visuals seem to be shared across space and time.
This article will explain the science of psychedelic visuals, the types of psychedelic visuals (e.g., closed-eye vs. open-eye visuals), and how different psychedelic drugs provide a spectrum of visual experiences.
What Are Psychedelic Visuals?
Visual effects are often one of the most prominent features of a psychedelic experience. When you hear the word “psychedelic,” your mind might associate it with colorful and intricate patterns.
There is a huge range of visual effects that you might experience with the use of psychedelics, but they fall generally under four categories: enhancements, distortions, geometry, and hallucinations.
The Science of Psychedelic Visuals
There is a lot going on in the human brain when psychedelic visuals occur.
Activity at the 5-HT2A Receptors
The effects of classic psychedelics, including visual effects, are mediated by their action at serotonin 5-HT2A receptors. They act as agonists at these receptors, which means they bind to them and cause them to produce a biological response, thus mimicking the role of the endogenous neurotransmitter–serotonin in this case.
We know this activity is responsible for psychedelic visual effects because the administration of the drug ketanserin (which is a 5-HT2A antagonist) both before and during a psychedelic experience blocks psychedelic effects, including perceptual distortions and hallucinations. (In chemistry and medicine, an antagonist is a substance that stops the action or effect of another substance. Since ketanserin is a 5-HT2A antagonist, it prevents classic psychedelic molecules from activating the 5-HT2A receptors.) Multiple studies have produced these results.
Geometric Visual Effects Relate to the Architecture of the Brain
In a 2002 paper, a group of researchers refer to the work of German psychologist Heinrich Klüver, who organized geometric visual hallucinations into four groups, called form constants:
Tunnels and funnels
Spirals
Lattices, including honeycombs and triangles
Cobwebs
In most cases, geometric psychedelic visuals are seen with both eyes and move with the eyes. The researchers in the 2002 paper interpret this as meaning that psychedelic visuals are generated in the brain. They theorize that hallucinations originate in the primary visual cortex (area V1), the area of the cerebral cortex that is essential to the processing of visual stimuli. The architecture of V1, in other words, determines the geometric effects you see during a psychedelic journey.
These researchers modeled the primary visual cortex as a lattice of interconnected hypercolumns or blocks that contain “all the machinery necessary to look after everything the visual cortex is responsible for, in a certain small part of the visual world” (Hubel, 1982).
Each of these hypercolumns is comprised of a number of interconnected columns that correspond to different orientations. These orientation columns display what is known as a shift-twist symmetry, while the hypercolumns display a lattice symmetry. The researchers use this symmetry to show how form constants can emerge when V1 is stimulated, such as by psychedelics. They also note that “the cortical mechanisms which generate geometric visual hallucinations are closely related to those used to process edges, contours, textures and surfaces.”
The neurobiologist Jack Cowan, who was involved in the 2002 study and is an expert on geometric visual hallucinations, previously suggested in a 1982 paper that activity moving across the visual cortex could be responsible for the experience of seeing or moving through a tunnel. This is due to the way that the retina maps onto the surface of the visual cortex.
The architecture of the brain is also fractal by nature, meaning that the same patterns repeat at different scales. This could help to explain why people often report fractal visuals when working with psychedelics.
As renowned psychedelic researcher Robin Carhart-Harris states in reference to psychedelic visuals:
Like tree branches, the brain recapitulates [itself]. You are not seeing the cells themselves, but the way they’re organized – as if the brain is revealing itself to itself.
Perceiving or traveling through different dimensions, meanwhile, might be the outcome of geometric hallucinations varying in the three dimensions of space and in time.
The Science of Psychedelic Visuals: Hierarchical Ordering of Brain Networks
The “relaxed beliefs under psychedelics” (REBUS) model, proposed by Carhart-Harris and Karl Friston, focuses on the notion of brain networks being ordered in a hierarchy. Networks like the default mode network (DMN) and central executive network (CEN) are higher-level networks, while areas like the hippocampus and visual cortex are seen as lower-level.
According to the REBUS model, this hierarchical ordering collapses under the influence of psychedelics. Higher-level networks like the DMN and CEN lose control over the lower-level regions. This loss of control allows the lower-level regions to act in an unconstrained way, which can result in many visual effects that you may experience when journeying with psychedelics.
Normally, lower-level regions like the visual cortex make predictions about our sensory input, and these are compared with our actual sensory input to see if those predictions are correct. This comparison helps our brains to construct an accurate model of the world, which is of course evolutionarily advantageous.
However, prediction errors can occur, which are the differences between predicted and actual sensory input. When these prediction errors originate from lower-level systems, the higher-level systems ordinarily update them since they have that top-down control.
But under the influence of psychedelics, the higher-level regions lose that control. This means that prediction errors from lower-level regions can, as Carhart-Harris and Friston state, “find freer register in conscious experience, by reaching and impressing on higher levels of the hierarchy.”
They add that “this straightforward model can account for the full breadth of subjective phenomena associated with the psychedelic experience,” including “entity encounters,” “eyes-closed dreamlike visions,” and “geometric hallucinations”.
According to the REBUS model, [the brain’s] hierarchical ordering collapses under the influence of psychedelics. Higher-level networks like the DMN and CEN lose control over the lower-level regions. This loss of control allows the lower-level regions to act in an unconstrained way, which can result in many visual effects that you may experience when journeying with psychedelics.
The Role of the Thalamus in the Science of Psychedelic Visuals
Another theory – the thalamic filter model – suggests that the main effects of psychedelics are related to the function of the thalamus and its relation to other areas in the brain. This theory is also known as thalamic gating or cortico-striatal-thalamo-cortical gating (CSTC).
The thalamus is like a relay station for pretty much all sensory information. Normally, the thalamus restricts certain information from entering the rest of the brain, such as the visual cortex.
However, according to the CSTC or thalamic gating theory, psychedelics prevent this inhibition of information flowing from the thalamus to other brain regions. The result is that we experience sensory data in a raw and unprocessed way.
Dreaming While Awake
A 2019 study published in Scientific Reports found that DMT creates an experience that is like “dreaming while awake,” in the words of Carhart-Harris. This study, led by Christopher Timmermann, was based on the use of an electroencephalogram (EEG) to measure brain waves (synchronized electrical pulses from masses of neurons).
Under the influence of DMT, participants experienced a reduction in alpha waves (which the brain produces while we’re awake). This was observed alongside increases in delta and theta waves, which are associated with dreaming.
As in the dream state, people on DMT are cut off from external reality while being immersed in what feels like another world. In a Newsweek article, Timmermann said:
“We saw an emergent rhythm that was present during the most intense part of the experience, suggesting an emerging order amidst the otherwise chaotic patterns of brain activity. From the altered brainwaves and participants’ reports, it’s clear these people are completely immersed in their experience—it’s like daydreaming only far more vivid and immersive, it’s like dreaming but with your eyes open.”
Entities and the Evolved Brain
The brain is an evolved organ. It is primed to detect certain things in the environment, endowing us with innate psychological tendencies.
The anthropologist Michael Winkelman wrote a 2018 paper that examined entities seen in psychedelic states from this evolutionary perspective. He discovered that ayahuasca and DMT entities were similar in nature to our ideas of gnomes, dwarves, elves, angels, and aliens. He believes that psychedelic entities “exemplify the properties of anthropomorphism, exhibiting qualities of humans.”
Winkelman argues that the various features of psychedelic entities reflect aspects of our brain function that evolved to our advantage.
These innate faculties include:
Agency detection: We are biologically programmed to detect predators, prey, and allies, even in objects and events where they do not exist or are unlikely to exist.
Anthropomorphism: The tendency to attribute human characteristics to non-human animals, natural features, or events.
Theory of Mind (ToM) or mind reading: Inferring the mental states – such as intentions, thoughts, and desires – of others. This helps us to explain and predict their behavior.
If psychedelics like DMT activate these faculties, then this might help account for the human-like appearances and behaviors of psychedelic entities. The brain also tries to detect patterns in ambiguous stimuli. (We previously saw how face pareidolia is a type of psychedelic effect; this tendency offers us an evolutionary advantage.)
If psychedelics activate this tendency, along with the others noted by Winkelman, then this could help explain the entities that many people encounter. The added effect of geometry might also help explain some of these entities’ strange or complex features.
