Enzymind Labs

Vision dynamics and hallucinated patterns

A set of links related to commonly percieved patterns that are different from visual stimulus patterns, and how they might be related to cortical implementation of human vision.

I like the speculation that our visual system is always making up patterns, and the sensory data we get "pushes" these patterns into some kind of closest match, sort of like video feedback. Oliver Sachs has an interest in this too. Here's a couple of quotes about pattern generation, in particlular the first one about very regular tesselation-like patterns.

Sachs' book "Migraines" includes a few first hand depictions of migraine aura phenomena.

Imigraine.Net includes images of scintillating scotomata.

The Migraine Aura Foundation page of depictions of aura

Exploring the visual hallucinations of migraine aura: the tacit contribution of illustration, a nice discussion of "fortification spectra" or scintillating scatoma typical of migraine aura, with many interesting first-person renderings.

G. D. Schott, Brain 2007 130(6):1690-1703

"... This article explores the unique contribution that illustration has made to understanding mechanisms subserving the visual aura."

Hollister (Hop) David, in commenting on his habit of finding patterns in pseudo-random textures:

"When painting semi-chaotic random textures like clouds, my mind will "recognize" shapes. Like a Rorschach ink blot. The shapes can be birds, faces, letters, symbols or geometric designs. Thus "The Tapestry of Rorschachery" emerges.

From page 100 of "Escher on Escher", Escher writes:

"... I found one suggestion in the writings of Leonardo da Vinci. This is the fragment, translated as best I can: 'When you have to represent an image, observe some walls that are besmeared with stains or composed of stones of varying substances. You can discover in them resemblances to a variety of mountainous landscapes, rivers, rocks, trees, vast plains, and hills. You can also see in them battles and human figures, strange facial features and items of clothing, and an infinite number of other things whose forms you can straighten out and improve. It is the same with crumbling walls as it is with the sound of church bells, in which you can discover every name and every word you want.'"

I have used just this process to find every Escher-like tessellation I've invented. In "Escher-like Monkeys" the monkeys move from abstract two dimensional tessellations to realistic three dimensional creatures much like the lizards in Escher's print "Reptiles".

Hop David pointed to his animated depiction of his visual aura, typical of migraine aura:

"...an attempt to portray something that was almost blinding me a few weeks ago. But for me these flashing patterns never precede headaches, thank God.

The flashing colors seem like a different phenomenon from the tessellations and geometric designs seemingly embedded in random textures. I used to see those a lot in my misspent youth when I'd indulge in illegal substances. I've been sober for decades but I can still bring them forward with an effort of will. They also come forward when I've gone longer than 24 hours without sleep."

and

"Is it possible a layer of neurons in the brain contain visual data enhanced with pattern recognition routines? I like to imagine a science fiction scenario where sensors in the brain record a raster image from this layer and then display the image on a screen the subject's viewing. That could make for interesting feedback."

Lorem Ipsum made a similar depiction and description in "Migraine aura", and points to other examples:

"This is a neurological phenomenon, occurring somewhere within my nervous sysem, probably the visual cortex. It is not to be confused with other claimed phenomena supposed to happen in the outside world. It is probably related to migraine headaches, which fortunately I'm not subject to. For me the aura is a purely visual experience, not accompanied by pain, dizziness or other symptoms. It doesn't interfere with normal vision, but is distracting. Your mileage may vary; for some people, it's a prelude to an actual headache.

I never saw an aura, so far as I can recall, until about age 38. After that it occurred at intervals of several years, and thereafter with increasing frequency.

The phenomenon is a process that takes perhaps 5 to 15 minutes to complete. It starts small and gradually expands to span the visual field. It is impossible to examine in detail because it is always at a fixed, off-center location within the visual field; if I try to look at it, it moves away. (That is one clear demonstration that it is internal, not in the outside world.)

The background color is the dark, nondescript color I see when I close my eyes. It may include afterimages from whatever I was looking at just previously. The brightly colored bands are not stationary but move like ripples in water. The separation into triangular regions with ripples moving in orthogonal directions is interesting; I have no explanation for it (except that the phenomenon is clearly a kind of oscillation, similar to the squeal of an audio system with feedback from speaker to microphone). The pattern is sometimes described as a zigzag line, but to me that description is inadequate. Among the moving bands of light there is often a brightest band, which may accidentally connect with the brightest band in an adjacent triangle, giving rise to the the impression of a zigzag line, but that ignores most of what is happening.

For a long time I didn't know what the phenomenon was called, but then came across a description of it somewhere on the web.

Having learned the medical term for it, I can easily find other attempts to represent it artistically. Here's the closest I've found to my own experience, shown with the eye open:[link]

Here's another. Here it's call ophthalmic migraine: (Broken [link])

It is always represented as a C-shaped region containing angular shapes. It may or may not be significant that all images I've seen so far show it curving the opposite way from mine, i.e. around the left side of the visual field.

I have to suspect those drawings were made by someone other than the person who had actually seen the aura, working from a verbal description.

Best drawing yet: (Broken [link]) "

From a journal entry of his:

The Migraine Aura Foundation page of depictions of aura

One of the animations shown here, the one with background photo showing expressway bridges, resembles what I see in a certain way -- to wit, I can concoct a verbal description that fits both the animation and my subjective experience:

There is an overall pattern that evolves slowly, over a period of several minutes, growing larger over time. At any moment, the detailed pattern is not static but exhibits a rapid shimmering, rippling motion in rainbow colors within each of a collection of geometric shapes.

But that description could fit a lot of experiences. My experience of migraine aura is different from this animation. In my experience, the geometrical shapes seem always to be triangles. They don't vary much in size, and they don't overlap or move around. The ripples within them don't vary in wavelength, but they do vary in direction.

I still want to make an animation of my own to show what I mean, but I need to acquire the appropriate skills. The means I have for 3D animation would be overkill, this is decidedly a 2D job. I don't want to use Flash. I've been working with SVG recently, and I've discovered that SVG animations can be driven by Javascript. That's probably the right medium to use."

Lorem Ipsum's depiction and description of the time course of migraine aura:

Migraine aura 2

Migraine aura 3

 

Blake Stacey's blog entry Physics Makes a Toy of the Brain, points to several interesting ideas and references related to this topic:

"...ideas from statistical physics can tell us important facts about our own brains. By studying the recurring motifs of hallucinations, we can construct a geometry of the mind."

 

"In the 1920s, long before the days of review boards and modern regulations for human experimentation, the neurologist Heinrich Klüwer ingested mescaline and recorded his observations. He reported visual hallucinations of four distinct types, which he called "form constants." These form constants included tunnels and funnels, spirals, honeycomb-like lattices and cobweb patterns. Similar structures have been reported with other drugs, like LSD; these same form constants also appear during migraines, in "hypnogogic" (falling asleep) and "hypnopompic" (waking up) states, when pressure is applied to closed eyes, and even in ancient cave paintings."

 

"In the late 1970s, [Jack] Cowan began to suspect that the culprit was not mescaline or LSD itself, but rather the visual cortex at the back of the brain, and in particular the section known as the primary visual cortex, V1. (In technical terms, this means focusing on topological rather than hodological hallucinations, studying those which might arise from a specific part of the brain rather than from malfunctions in the connections among multiple regions.) ... Cowan realized, to a decent first approximation, the visual cortex could be treated mathematically as a uniform surface, essentially a flat plane."

 

"What patterns of activity would arise when this patch of brain-stuff is perturbed by some outside influence? The answer lies in V1's symmetry: no matter where you stand over it, it looks roughly the same. Shift (or translate) it left or right, and it appears unchanged. To a mathematician, this approximate "translational symmetry" carries a direct implication: the natural patterns or "eigenmodes" of neural activity moving across the cortex will be plane waves.

Imagine a wave whose crest is a straight line, rippling placidly across a tank of water. The situation in V1 is much the same, except that instead of the displacement of water, the quantity of interest is the neural activity at a given point. In physics jargon, the set of all points and their associated neural firing rates constitutes a field, and the variation over time of that field is tractable via the tools of field theory.

Oddly enough, this thread of the research stretches back to Alan Turing [he studied possible mechanisms of morphological development of patterning based on chemical dynamical systems] ..."

"The relationship between the eyes and the visual cortex is an interesting one, with significant ramifications. It is not the case that, if a square is projected onto the retina, the cortical columns in V1 will "light up" in a square pattern, like the image from a camera being reproduced on a television screen. Instead, a more sophisticated "mapping" exists between our field of view and our primary visual cortex, a relationship known as a complex logarithmic map. A complex logarithm turns circles into straight lines, for example, so that if we stare at a light circle on a dark background, a straight line of neural activity will cut across V1. (If two lines meet at an angle, a complex logarithmic map will turn them into two other lines meeting at the same relative angle. This is a type of conformal map, which preserves angles locally but distorts shapes at larger scales.)"

"The logical question is then, what images seen by the eyes correspond to the eigenmodes characteristic of the perturbed V1? What would you have to see for the ordinary activity of V1 to look like the patterns seen when the brain is perturbed by a migraine or a drug?

The answer is that the eigenmodes of this simple model correspond to two of Klüver's form constants.

...  Shapes seen in hallucinations arise naturally from the symmetries of V1."

Jack Cowan at MIT: Cowan is a pioneer in mathematical neurophysics, is developing sophisticated physical models of the behavior of neurons in the brain. He is a co-originator of the Wilson-Cowan equations to model neural behavior, and his students and collaborators have been thinking recently about hallucinations and other emergent properties of the brain.

"We have recently found a way to describe large-scale neural activity in terms of non-equilibrium statistical mechanics [Buice & Cowan, in preparation]. This allows us to calculate (perturbatively) the effects of fluctuations and correlations on neural activity. Major results of this formulation include a role for critical branching, and the demonstration that there exist non-equilibrium phase transitions in neocortical activity, which are in the same universality class as directed percolation. This result leads to explanations for the origin of many of the scaling laws found in LFP, EEG, fMRI, and in ISI distributions, and provides a possible explanation for the origin of alpha, beta, gamma, delta and theta waves. It also leads to ways of calculating how correlations can affect neocortical activity, and therefore provides a new tool for investigating the connections between neural dynamics, cognition and behavior."

“Spontaneous pattern formation in large scale brain activity: what visual migraines and hallucinations tell us about the brain” (2006).

Also see “Hallucinatory neurophysics” at Sean Carroll’s old blog, Preposterous Universe.

"[H]ere is the punchline: patterns of hallucinations reflect normal modes of the neurons in the visual cortex. By "normal modes" we mean the characteristic patterns of vibration, just as for a violin string or the head of a drum. The idea is that a drug such as LSD can alter the ground state of the visual cortex, so that it becomes excited even in the absence of stimuli. In particular, certain oscillating patterns can appear spontaneously. Generally these would take the form of different configurations of straight lines in the cortex itself; however, due to the distortion in the map from our visual field to the brain, these appear to us as spirals, tunnels, and so on. Indeed, Cowan and collaborators have shown that these normal modes can successfully account for all of the basic forms of hallucination classified by Kluever decades ago.

 

2008-11-30  I've been tinkering with triangular tilings, have a splitting migraine headache, and decided to search devaintART tags on the term "triangular tiling". All five results were of my images! There are upward of 50 million pieces indexed on this site, and I'm the only one that used this common nomenclature, although there are undoubtably 10's of thousands of pieces that utilize a triangular tiling for composition. I tried a search on "hexagonal tiling", and two of eight were my pieces. (I have more pieces than this related to hexagonal tiling, I just didn't tag them with this term).

It is interesting that of 10's of thousands of artists at this site, two of them most deeply into tilings and tesselations, Lorem Ipsum (who has one of the nine pieces tagged "hexagonal tiling" ) and Hollister (Hop) David, mentioned and quoted above, have both described visual aura associated with migraine (both without headache, acephalgic migraine, and without reporting "periodic filling in" patterns that are more rarely associated with migraine). And myself makes three. Why this extraordinary coincidence? Partly it is a selection bias -- I find artwork that I am interested in.

After a cursory search I don't find anything that indicates M. C. Escher or Leonardo da Vinci experienced migraine or visual aura. But here's an interesting, but tenuous, link between da Vinci's mirror writing and migraine:

A second Leonardo da Vinci?

We describe a young woman who suddenly began mirror writing with her right hand and has not reverted to normal writing for more than 6 years, although she writes normally with her left hand. She is ambidextrous, although she had previously used only her right hand for writing and drawing. Since it is much easier for her to use right-handed mirror writing, she uses her left hand only for writing meant to be read by others and her right hand for all other writing. Her hobbies are sculpture and painting, and her chief complaint is migraine accompanied by sensory and perceptive disturbances.

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