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It's well-known that psychedelics can provoke hallucinations. Scientists have spent over a century investigating this chemical reaction and its potential insight into the brain’s circuitry.
Now, a possible explanation is emerging and it has to do with evolution. Hallucinogens, such as LSD, seem to disrupt filtering mechanisms that the brain implements, which can produce random signals to be amplified. The science is fascinating and tells us a great deal about the human brain.
Interested to know more? Click through the gallery.
Heinrich Klüver, a young perceptual psychologist at Harvard University, tested psychedelics on himself for a study on visual hallucinations.
Klüver consumed a peyote button, which comes from a dried cactus, and proceeded to document changes to his visual field.
He saw patterns that reminded him of Joan Miró paintings and even ancient cave art. He classified the patterns into four categories: tunnels, spirals, lattices, and cobwebs.
Half a century later, a researcher at the University of Chicago, Jack Cowan, sought to reproduce those patterns mathematically, as he believed it would provide insight into the brain’s circuitry.
In 1979, Cowan reported that “the electrical activity of neurons in the first layer of the visual cortex could be directly translated into the geometric shapes people typically see when under the influence of psychedelics.”
What does this mean? Well, according to Cowan, when we hallucinate, what we see is a reflection of the brain’s neural network.
Cowan’s theory is linked to what’s called “Turing patterns.” In the 1950s, mathematician Alan Turing (pictured) hypothesized that repeating patterns seen in biology are tied to a mathematical mechanism.
Recent research by physicist Nigel Goldenfeld takes Turing’s patterns to the next level, arguing that the mechanism is behind the geometric forms that people see when they hallucinate.
Essentially, the patterns that we see are enthusiastic neurons in the visual cortex. Light reflects off of objects that we see. When the image enters our eyes, the retina focuses in.
The retina (pictured) is lined with what are called photoreceptor cells that essentially take the light that they absorb and convert it into electrochemical signals.
These signals make their way to the brain, which stimulates neurons in the visual cortex. This means that what we see when we hallucinate are patterns of light reflecting off of the objects that are in our view, mixed with a “random firing of neurons in the cortex.”
In the brain, the number of neurons that are activated randomly waver. When an inhibitory neuron turns on, it actually causes neurons that are close by to turn off.
According to the science, connections between inhibitory neurons are long-range, even those that are sparse. So if they’re firing off faster than random signals, that’s when the Turing patterns emerge.
Hallucinogens, such as LSD and psychedelic mushrooms, seem to disrupt the brain’s normal filtering mechanisms, which can amplify long-range inhibitory connections. This allows all the random signals to be boosted, as well, which furthers the Turing effect.
Evolution has developed a specific network structure that prevents hallucinations from happening at any time.
This development is important for humans because it helps us distinguish between something like a snake, which could be of danger to us, and just a general spiral shape.
If the cortex had developed to have more long-range connections, it would be quite difficult for us to make the distinction between shapes and objects.
Our tendency would be to form patterns in our brain, instead of processing all the visual material that we absorb.
An experiment conducted on models demonstrates that spontaneous patterns won’t form unless they are forced to. And that’s exactly what happens when under the influence of hallucinogens.
Philosopher Jean-Paul Sartre experimented with hallucinogens himself and found that his visual perception could be distorted for weeks on end.
Sartre reported seeing distorted clocks that appeared as owls. He also saw crabs that were apparently following him constantly during these hallucinations.
These visions are more complex than Klüver’s categories. This is because a higher cognitive function may be activated, which can include memories.
What does this do? As hallucinations become more complex, the brain desperately tries to make sense of what it’s seeing.
Researchers argue that what emerges are spontaneous memories that begin to arise as the “higher brain” becomes more engaged.
Klüver reported that some of his research subjects also reported what’s called “tactile hallucinations.”
Tactile hallucinations are hallucinatory experiences such as the perceived sensation of cobwebs dragging across the research subject’s skin, for example.
Other researchers believe that because of the cobweb pattern that can emerge visually as part of the hallucination, the somatosensory cortex (highlighted in purple) also produces the sensory experience.
That kind of hallucinatory experience can also be furthered into auditory hallucinations, which explains things like tinnitus.
Why is this revelatory in the scientific context? The theory of hallucination applied to visual experiences can be applied to other senses, too.
Sources: (Quanta Magazine)
See also: Alice in Wonderland syndrome is actually a real neurological condition
The mathematical theory behind hallucination
Disrupting the brain's normal filtering mechanisms
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It's well-known that psychedelics can provoke hallucinations. Scientists have spent over a century investigating this chemical reaction and its potential insight into the brain’s circuitry.
Now, a possible explanation is emerging and it has to do with evolution. Hallucinogens, such as LSD, seem to disrupt filtering mechanisms that the brain implements, which can produce random signals to be amplified. The science is fascinating and tells us a great deal about the human brain.
Interested to know more? Click through the gallery.