Synesthesia, afterimages

A couple of weeks ago, I had an experience that might be classified as synesthesia. First I’ll describe it, then I’ll explain how the details imply an explanation for synesthetes, if it was in fact an instance of synesthesia.

I was out for a run late in the evening. I’d gone three miles and had about half a mile left. At this point in my route there’s a pretty hefty hill to run up, which I took at a good clip. Afterward I was breathing heavy but not unusually so; the lack of oxygen getting to my brain probably has something to do with causing the experience. If I had any sense at all, I would have tried to isolate the sensory stimulus causing the image, but I didn’t think of it at the time.

In the center of my visual field what looked like an afterimage appeared, although it couldn’t have been an afterimage proper because there had been no visual stimulus to cause it. It just showed up. In shape the image was shaped like two guitar picks, one pointing up and one pointing down, with a little space in between them. They took up about 20 degrees of my visual field, vertically, and maybe 5 degrees horizontally. The color was incandescent yellow-white, exactly like the afterimage that you’ll see if you look too long at a light bulb. This is why I make the connection to afterimages. This vision lasted for about a minute and then faded. Notably, I did not experience this as emotionally meaningful in contrast with most synesthetes (except in terms of intellectual curiosity), but this may be due to my highly unusual emotionality.

Some context for the more theoretical part coming up next:

Negative afterimages are caused when the eye’s photoreceptors, primarily known as rods and cones, adapt to overstimulation and lose sensitivity. Newer evidence suggests there is cortical contribution as well.[3] Normally, the overstimulating image is moved to a fresh area of the retina with small eye movements known as microsaccades. However, if the image is large or the eye remains too steady, these small movements are not enough to keep the image constantly moving to fresh parts of the retina. The photoreceptors that are constantly exposed to the same stimulus will eventually exhaust their supply of photopigment, resulting in a decrease in signal to the brain. This phenomenon can be seen when moving from a bright environment to a dim one, like walking indoors on a bright snowy day. These effects are accompanied by neural adaptations in the occipital lobe of the brain that function similar to color balance adjustments in photography. These adaptations attempt to keep vision consistent in dynamic lighting. Viewing a uniform background while these adaptations are still occurring will allow an individual to see the after image because localized areas of vision are still being processed by the brain using adaptations that are no longer needed.

This effect isn’t restricted to light and color, it’s also related to perceptual processing. If you watch a waterfall for too long and then look at a brick wall, the bricks will appear to move upwards because of the same sort of perceptual fatigue, with respect to processing motion.

Putting all of these pieces together, I figure this explains the mechanism for synesthesia. When a synesthete experiences synesthesia, it’s accompanied by a rather shocking loss of blood flow to large portions of the brain, to an extent that would typically suggest brain damage. It seems reasonable to me that loss of blood flow to a region related to a particular sort of perceptual processing would artificially cause this sort of afterimage fatigue. For instance, loss of blood flow to the visual cortices in the regions that process “red” and “dots” would cause a person to see green dots, like an afterimage.

If this is correct, it implies that something in the brain is miswired to turn off blood flows upon perceiving particular stimuli, or something similar to depress electrical activity. E.g. Upon processing the number ‘7’, a synesthete’s brain might turn off the blood supply to the neurons that correspond to “red” in that part of the visual field, causing it to appear green.

Aside from all of that, I want a term for the screen within our visual field where things like afterimages are projected. This is also where the homonculus appeared during my misadventure with marijuana. If anyone knows of a name for this screen, I’d love to hear it.


About Aeoli Pera

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20 Responses to Synesthesia, afterimages

  1. Patrick says:

    It’s interesting listening to a description based upon body mind dichotomy explain sensort phenomenon in terms of secondary compounding ‘mind-like’ effects that result from ‘body-like’ stimulus such as blood flow.

    I think this is why we need meditation. Everyone can experience the link between body and mind of a deeper level I think.

    I’m in Vancouver RN. It’s a very INTJ city. I like it. I feel like they murder you extrajudicially in the proper sort of way.

    • Patrick Dualback says:

      By you I mean the Royal plural second person. Like personally I feel like if I were to thoughtcrime I’d want to do it here because you have a proper sort of thought police here. A really introverted and businesslike philosophical sort. Real Angus Beef.

    • Aeoli Pera says:

      >It’s interesting listening to a description based upon body mind dichotomy explain sensort phenomenon in terms of secondary compounding ‘mind-like’ effects that result from ‘body-like’ stimulus such as blood flow.

      Synesthesia is undoubtedly accompanied by blood flow loss in massive areas, it’s already ScIeNcE.

      >I think this is why we need meditation. Everyone can experience the link between body and mind of a deeper level I think.

      I have enough trouble praying with the way my focus wanders, meditation might be shooting for the moon.

  2. Lazer says:

    I see purple sometimes. I hypothesized once it may just be a burst of melatonin or some other tryptamine in the brain. Usually happens during high periods of stress when extreme focus is needed, or during twilight sleep. The purple is similar to the color indigo seen during deep meditation focus.

    • Aeoli Pera says:

      Can you be more specific?

      • dude says:

        It’s a photochemical protein some people call it an enzyme known as rhodopsin that is released by low/no light stimulus, which activates your night vision, it looks purple.

        Night vision is easy for me, it takes about 10 to 30 seconds, other friends it takes 1 to 3 minutes. Though I just read it takes some people 30 to 40 minutes to adapt to full night vision. Perhaps having no deficiencies of vit A helps in acquiring night vision at a faster rate, I guess. Perhaps I have an evolutionary adaption.

        Using your spatial vision (rod cells, which are also used for night vision) is also a warrior technique, it helps zeroing in on movement increasing your reaction time, not only that, it helps to recognise objects that are camouflaged.

        Meditation, I find this activates my ability to see qi anytime as well, basically activating my spatial vision. This was something I could do at the age of 4, didn’t know what it was at the time,now I’m exploring it.

        Aeoli, I was thinking perhaps you had a combination of Synesthesia vision and a trick involving the blind spots, hence your brain filling in the space. Maybe?

  3. Edenist Whackjob says:

    Have you been reading Personal Power Meditation?

  4. glosoli says:

    I very often see an image when my eyes are closed, but only in bright sunlight.
    It is like a translucent deep-sea dwelling creature, and it is always the same shape, so it’s not related to whatever I was looking at before I close my eyes. It’s quite small.
    If I look at it (with my eyes closed) it drifts off to the left or right, but if I don’t look at it, I can hold it still in the middle of my vision.
    It has always appeared benevolent, but from many hundreds of thousands of years ago, and I am always fascinated to gaze at it, wondering what it is.

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