What Causes Visuals In Psychedelic Trips?
I remember lying on my stain-filled college apartment carpet. I was fully expecting to see flying translucent dragons the first time I tried LSD, only to be disappointed when my psychedelic trip involved no complex visuals. Instead, my only visual was my roommate insistently telling me we ran out of Mountain Dew Baja Blast. So what causes visuals in psychedelic trips?
When it comes to sheer the inability of science to give coherent explanations, psychedelics’ ability to grant visuals during a trip is right up there in the pantheon of ill understood phenomena. Let’s not forget we’re using the brain to attempt to unravel the brain. It is a topological nightmare that inherently puts humans at a disadvantage. Yet, here we are on the verge of unpacking another audacious aspect of the psychedelic experience. So let’s have at it.
Before diving into the factors that may cause visuals in a psychedelic trip, it’s important to understand how your brain processes everything you’ve ever seen in your lifetime.
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Seeing (What You Think) Is Reality
We see with our eyes is not necessarily an accurate statement. This isn’t some intentionally provocative postmodern whatever you overhear at a coffee shop in Silverlake — it’s just science.
Vision is a computational beast. Over 50 percent of our cerebral cortex is solely dedicated to processing visual information. It sounds like a lot. But when you consider light travels nearly 100,000 times faster than the quickest signal in the human body, that enormous percentage isn’t so daunting. The stacks of neuroscience books required to fully understand how vision works is colossal. And you shouldn’t be expected to know everything about this process. However, I’ll condense years of courses in just a single paragraph.
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Light travels to the eyes, but not every cell within the eye responds to light. So the retina converts it to a signal so the rest of the brain can understand it. Only about a million cells carry information from your retina to your brain. Which surprisingly makes your eyes only a one megapixel camera.
This journey of visual information from your eyes to the occipital lobe is called the retinofugal pathway. (Which is the back of your head where the visual cortex is located.) This is the final destination of vision, but it’s not a straight shot. Like all epic journeys, side quests happen in the retinofugal pathway. Visual information goes to a variety of places before your brain can even recognize what you see. Aside from places like the optic nerve and the optic chiasma (where visual information from your left eye goes to the right side of your brain and vice versa), visual information also goes to the thalamus which is basically a relay station for the entire brain.
Nearly all sensory information, everything you’ve ever seen and heard, goes through the thalamus.
Eventually the visual information leaves the thalamus and goes to the visual cortex (the occipital lobe.) Which finally allows you to actually “see” whatever you’re looking at.
Seems pretty logical, but the brain is in no obligation to operate how we think it should operate. Before I started writing this article, I asked all the incredible people that follow me on Twitter if there was a single unifying theory of psychedelics. The question sparked a ton of replies. But ultimately the question transformed into: is there even a single unifying theory of the brain?
In relation to how psychedelics modulates our visual field, I would say yes — but not a single unifying concept. Actually, three concepts:
- The brain is a prediction engine
- The brain operates on hierarchy
- And, the brain excels at auto-correction
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The Prediction Engine
Earlier I mentioned we don’t necessarily see with our eyes. And it’s mostly because our brain attempts to predict what it sees before it actually sees it.
So why would our brain try to predict what we see and how does all of this relate to psychedelics? Well, a lot of reasons. Our brains are evolutionarily adapted to coordinate our bodies for survival.
For example, when something in our field of vision is imminently dangerous, in certain instances the visual information coming from the eyes doesn’t have time to complete the entire retinofugal pathway. The thalamus relays the information directly to the amygdala. (Which is a multi-faceted part of the brain that’s generally associated with processing fear.) And it instructs our body to run away from whatever is dangerous before we even see what the danger is.
Even the stuff we see (information that gets to the visual cortex) actually gets sent back to the thalamus. It then goes back to the visual cortex — almost like a mental validation system.
Think of it as a CAPTCHA for consciousness.
In fact, an area of your thalamus called the Lateral Geniculate Nucleus (LGN) is a powerhouse for visual processing. Surprisingly, a large portion of the neurons found inside the LGN receive information coming back from the visual cortex. It’s like the equivalent of a movie screen receiving information from the projector. But sending most of that movie back to the projector from the screen itself.
Admittedly it’s a process that is poorly understood by science but it does indicate a feedback in our visual system. An example of thalamocortical circuit or loop.
At any given moment, your brain is constantly constructing your outer world, or reality, based on probabilistic models.
These world models are auto-generative, constructed from a facet of things like your knowledge of how basic physics works, evolutionary adaptations, expectations of the origins of sensory stimuli and a list of other factors that are too numerous to include. Imagine sitting in an office cubicle while casually observing a mundane day at work.
Your brain doesn’t have to perpetually calculate the size of your desk because it’s a constant that usually never changes. The colors of the white fluorescent lights above your cubicle do not need to be meticulously evaluated every millisecond. Because the probability of these lights suddenly shifting hue is nearly impossible. Your brain knows this, and it constructs models that operate on sheer probability and likelihood. And it generally does a pretty good job.
The Brain Operates On Hierarchy
Your brain predicting reality also operates on a level of hierarchy. This hierarchy is reflected in how the sensory areas of the brain are organized. In the case of your visual cortex, it’s a multi-layered hierarchical pile of gooey cells.
Your visual cortex is arranged from your primary visual area (V1), V2, V3, Middle Temporal Area (MT, also called V5) and finally the Inferior Temporal Cortex (IT, also known as V6). The first layer, V1, allows for basic visual detection.
Essentially the shapes of objects and each subsequent layer in the visual cortex hierarchy reveals a higher complexity of detection. IT/V6 allows for incredibly detailed visual perception, like recognizing fine details in faces.
We know this is the case because when these systems get damaged, it can result in very distinct disorders.
For example, damage to the V1 can result in the inability to see in a part of the visual field. Basically a blind spot. Surprisingly, even in blind areas, a person can still respond to visual stimuli, or “blindsight”.
Whereas damage to a deeper part, like IT will result in a person being able to discern the shape of a face, but completely unable to recognize faces. Which is a condition called prosopagnosia — face blindness.
Although these six visual layers may seem to operate in a classic hierarchy. A chain of events in which V1 passes information to V2, then so on until it gets to IT/V6 — that’s not necessarily the case. Once again, the brain is weirdly fascinating, and above all else, it’s going to do whatever it wants to do. Quite often, information going down the hierarchy actually goes back up, then down again.
For example, the LGN inside the thalamus may project visual information to V1, then jump to V4, only to go to V2 as its final destination. Sometimes information from the LGN skips V1 altogether and goes directly to and goes back to V1.
This jumbling of hierarchical visual information may seem chaotic. But it’s necessary to validate initial predictions made by our brain of our visual field. And if the prediction doesn’t match up, it can correct these assessments with the actual sensory information. In fact, your brain has a built-in auto-correction that rivals every version of Microsoft Word that’s ever been released.
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Excellent At Auto-Correction
Even your brain occasionally has processing and predictive errors. And while it does its best to accurately predict the universe around you, it does make mistakes.
However when those mistakes are detected, your brain does a remarkable job correcting those errors.
Imagine your brain is a soccer analyst, making predictions on a game they’re going to commentate on.
The soccer analyst (your brain) is writing notes to predict how they expect the game (your visual reality) to play out. Precise calculations of each player are being analyzed. The habits of their playing ability, the results of past games against similar opponents. And even how the weather will affect the pitch and each team’s performance in adverse conditions.
These notes will help the analyst (your brain) call the game better by having a blueprint of likelihoods that could happen in the game. This means less manual work when it’s gametime — conserving energy. Working smart, instead of working hard. When the game finally starts (being exposed to sensory stimuli), the analyst (your brain) is able to call the game (your visual reality) based on the notes that were written before the game even started.
Occasionally the notes may not match up with the actual game.
Let’s say a player suffers an injury right before the game or the home team accidentally wears the away jerseys. The analyst sees the error in their notes, looks at the game to confirm their notes (predictions) are incorrect and changes their notes. It then calls the game accurately according to how the sensory stimuli (the game) matches up with the predictions (the notes).
It’s theorized the brain is always in a subtle but persistent level of auto correction. It is a never ending dance of going up and down (and then back up) the chain of visual hierarchy. Redundantly checking predictions against sensory information.
It’s believed that task-evoked responses (like picking up a twig in the forest, if you’re into that sort of thing) makes up for only 0.5-1 percent of the brain’s overall energy budget. With the rest believed to be in a vigilant state of hierarchical prediction/correction.
There’s evidence that our brains are so preoccupied with this process that it’s filled with seemingly pre-constructed models of our visual world that we defer to. Especially when the level of stimuli is not adequate or all together absent. Neurologist Marcus E. Raichle called this unaccounted brain consumption “dark energy” in the sense that we know it’s there. But we don’t know what it’s there for. It’s also known as ‘spontaneous brain activity.’
And it could be the key to understanding how we have visual experiences on psychedelics.
Tripping When We’re Not Actually Tripping
Science actually has a large trove of data from sensory experiments dating back from the 1940s. With William Grey Walter noting a level of spontaneous brain activity in his flicker experiment. This discovery of spontaneous brain activity spawned some pretty wild things. Like the Dream Machine, a stroboscope device created to “replace the television” and induce a “drugless high”.
It didn’t catch on — but it did show that our brains are capable of constructing patterns from rhythmic or oscillating visual stimuli.
But what happens to the brain when there is no visual stimulus — How can the brain assemble patterns and predict/correct stimuli that don’t exist?
An interesting study took place in 2004 in which researchers at Harvard Medical School wanted to look at potential visual hallucinations from prolonged blindfoldedness. Thirteen subjects endured 96 hours of continuous blindfolding (that’s five straight days without sight.) And at the end of the experiment, ten out of thirteen participants reported visuals that ranged from elementary to complex.
Some of these visuals were downright frightening. Like standing in front of a giant mirror and seeing a “green face with big eyes.” Others were bizarre like “Elvis toward the center, maybe a little off to the left side.”
In one particular instance, a person saw a menacing face in a ceremonial mask only while listening to Mozart. All these visuals were spontaneous in that the subjects couldn’t incite them or exert control when they were occurring.
In another study that looked at spontaneous brain activity in the absence of visual stimuli, the visual cortex of anesthetized and awake animal models (cats) were analyzed. Researchers concluded that even in complete aesthesia, representing the ultimate deprivation of senses, brains still arrange dynamic models that constantly switch in the expectation of sensory stimuli.
Research on spontaneous brain activity and the models that are constructed is still an ongoing interest in neuroscience. Eventually we will have more answers. But the data we currently have suggests that spontaneous brain activity has a strong correlation to the brain’s expectation of stimuli and in the process, develops visual information inside the visual cortex because of this.
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The One True Theory(s) Of Psychedelics
In order for us to understand this phenomena, we have to work backwards and find reasonable theories rooted in science. The starting point being: we see things and experience alterations of our visual field on psychedelics. You can call this hallucinations. But I’m sure the psychedelic linguistic police will write me a ticket for using antiquated terminology.
Working backwards from a visual trip, the inexplicable result of an acute dose of psychedelics, it’s easy to believe that the three universal concepts we’ve previously identified: Predictions, error-correction, and hierarchical information no longer have integrity and begin to unravel.
But perhaps this isn’t the case.
Initially I wrote this article with the intent of illustrating how psychedelics may represent a collapse or disorganization of these neurological mechanisms that generally define how we perceive our visual reality. This is part of an on-going trend with psychedelic neuroscience that systems. Especially in the Default Mode Network (DMN), tend to go towards a state of disarray when psychedelics come into play.
One of these concepts, Entropic Brain Theory, attempts to explain the subjective experience of a trip through the idea that psychedelics destabilize functional connectivity with certain networks in the brain which accounts for altered consciousness.
The general idea is the brain is operating around a state of “criticality” (with depressive states seen as a ‘sub-critical’) and psychedelics push our brains towards a critical state, which is represented by the beneficial properties usually associated with psychedelics (decreased depression and anxiety).
It’s an early theory (proposed nearly a decade ago). And one that is devoid of recent discoveries in psychedelic neuroscience – but still among the most popular.
There’s also REBUS, or ‘relaxed beliefs under psychedelics.’ It focuses on the idea of hierarchical ordering of neurological networks — assigning networks like the DMN and Central Executive Network (CEN) as a higher-level network while other areas, like the hippocampus and sensory areas (like the visual cortex), are seen as lower-level.
In the REBUS theory, while under psychedelics this hierarchy collapses — higher-level areas no longer exert the same influence it typically has on lower-level areas. This loss of inhibition allows for these lower-level areas to operate unconstrained and lead to some pretty trippy perceptual things that we experience on psychedelics.
Those theories suggest brain network-wide disarray.
With critical systems struggling to process psychedelics’ influence on sensory hierarchy approaching towards a state of complete neurobiological entropy. Sounds scary — but maybe the brain isn’t in such an impaired state.
In fact, what if the brain is being the computational powerhouse that it always has been. But operating with computations that haven’t been completely processed yet?
Another theory, thalamic gating (or cortico-striatal-thalamo-cortical gating (CSTC) for people that love to say long words) places the emphasis of the subjective nature of psychedelics on thalamus and its relation to all cortical regions in the brain.
As mentioned earlier, the thalamus is a relay station for nearly all sensory stimuli. Normally the thalamus would “gate” or restrict information from entering the rest of the brain (like the visual cortex).
However, in the CSTC/thalamic gating theory, psychedelics no longer inhibit the information flow from the thalamus to other cortical regions and we experience data in a raw, unprocessed, and error-filled way.
So what is it — which theory is correct? The only real answer is: we don’t really know.
Psychedelic neuroscience can still advance without claiming absolutes. We don’t have to pick “sets” and rep our theoretical territory with colorful bandanas (although it would be hilarious). This article was solely focused on which brain mechanisms may initiate visuals during a psychedelic trip.
But as many of you know “tripping” isn’t necessarily about what you see. These substances augment how a person thinks, the ability to judge the passage of time, episodic and working memory. Not to mention persistent changes that can last days, months, even years after an initial trip.
To believe any single theory can explain the multi-faceted ways in which psychedelics modulates cognition and neurobiological processes is naive.
The most likely reality is whatever happens to the brain while tripping is a combination of all three theories in some capacity, along with neuroscientific ideas that are yet to be discovered.
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What do I think is really happening?
There’s no way you would let me end this article without me telling you what I believe causes visuals from psychedelics. I knew what I was getting into when I started writing this thing.
Whatever is happening to the brain, it’s clear that it involves sensory hierarchy, sensory prediction, and error correction. Those fundamentals seem to be the neurological building blocks of how we perceive all stimuli. Even without psychedelics, alter those three processes and you’re in store for some extraordinary visuals.
In the case of psychedelics, I find it absolutely impossible that these substances would enact it’s mechanics on the brain without doing something to the thalamus. There are far too many 5-HT2A (serotonin) receptors and nuclei that project directly to sensory areas that are wedged into the 5.7 centimeters of the thalamus for it not to play a role in the subjective experience of psychedelics.
Also, I believe Manoj K. Doss’ new theory of the cortico-claustro-cortical model (CCC) playing a role in psychedelics deserves far more attention. In general, everything from Doss deserves more attention.
What Causes Visuals in Psychedelic Trips – In Conclusion
There are a lot of things regarding how our brains perceive visual reality that were intentionally left out due this article already being entirely too long. The existence of thalamocortical loops deserve an article, along with the pulvinar nuclei in the thalamus. Magnocellular, parvocellular, koniocellular neurons, ocular dominance columns, the free energy principle — all of this may have its place in explaining visuals during a psychedelic trip.
However, one thing is for certain in the realm of psychedelic scientific inquiry: Your supply of Mountain Dew Baja Blast should never avert the progression of an LSD trip. That very well could be the only root principle of psychedelics.