[BoxOfRain]

Isn't this idea demonstrably false due to the existence of various sensory disorders too?

I have a disorder characterised by the brain failing to filter own its own sensory noise, my vision is full of analogue TV-like distortion and other artefacts. Sometimes when it's bad I can see my brain constructing an image in real time rather than this perception happening instantaneously, particularly when I'm out walking. A deer becomes a bundle of sticks becomes a muddy pile of rocks (what it actually is) for example over the space of seconds. This to me is pretty strong evidence we do not experience reality directly, and instead construct our perceptions predictively from whatever is to hand.

[scoot]

Pleased to meet someone else who suffers from "visual snow". I'm fortunate in that like my tinnitus, I'm only acutely aware of it when I'm reminded of it, or, less frequently, when it's more pronounced.

You're quite correct that our "reality" is in part constructed. The Flashed Face Distortion Effect [0][1] (wherein faces in the peripheral vision appear distorted due the the brain filling in the missing information with what was there previously) is just one example.

[0] https://en.wikipedia.org/wiki/Flashed_face_distortion_effect [1] https://www.nature.com/articles/s41598-018-37991-9

[nervousvarun]

Only tangentially related but maybe interesting to someone here so linking anyways: Brian Kohberger is a visual snow sufferer. Reading about his background was my first exposure to this relatively underpublicized phenomenon.

https://en.wikipedia.org/wiki/2022_University_of_Idaho_murde...

[BoxOfRain]

Ah that's interesting, mine is omnipresent and occasionally bad enough I have to take days off work as I can't read my own code; it's like there's a baseline of it that occasionally flares up at random. Were you born with visual snow or did you acquire it later in life? I developed it as a teenager, and it was worsened significantly after a fever when I was a fresher.

Also do you get comorbid headaches with yours out of interest?

[scoot]

I developed it later in life. The tinnitus came earlier (and isn't as a result of excessive sound exposure as far as I know), but in my (unscientific) opinion they are different manifestations (symptoms) of the same underlying issue – a missing or faulty noise filter on sensory inputs to the brain.

Thankfully I don't get comorbid headaches – in fact I seldom get headaches at all. And even on the odd occasion that I do, they're mild and short-lived (like minutes). I don't recall ever having a headache that was severe, or that lasted any length of time.

Yours does sound much more extreme than mine, in that mine is in no way debilitating. It's more just frustrating that it exists at all, and that it isn't more widely recognised and researched. I have yet to meet an optician that seems entirely convinced that it's even a real phenomenon.

[BoxOfRain]

Interesting, definitely agree it likely shares an underlying cause with tinnitus. It's also linked to migraine and was sometimes conflated with unusual forms of migraine in the past, although it's since been found to be a distinct disorder. There's been a few studies done on visual snow patients, including a 2023 fMRI study which implicated regions rich in glutamate and 5HT2A receptors.

I actually suspected 5HT2A might be involved before that study came out, since my visual distortions sometimes resemble those caused by psychedelics. It's also known that both psychedelics and anecdotally from patient's groups SSRIs too can cause a similar symptoms to visual snow syndrome, I had a bad experience with SSRIs for example but serotonin antagonists actually fixed my vision temporarily - albeit with intolerable side-effects so I had to stop.

It's definitely a bit of a faff that people have never heard of it, I had to see a neuro-ophthalmologist and a migraine specialist to get a diagnosis. On the other hand being relatively unknown does mean doctors can be willing to experiment. My headaches at least are controlled well these days.

[cricalix]

scoot, you may find the current mini-series by the podcast Unexplainable to be interesting. It's on sound, and one episode is about tinnitus and research into it.

https://www.vox.com/podcasts/467048/unexplainable-hearing-au...

[scoot]

Thanks!

[numpy-thagoras]

The default philosophical position for human biology and psychology is known as Representational Realism. That is, reality as we know it is mediated by changes and transformations made to sensory (and other) input data in a complex process, and is changed sufficiently to be something "different enough" from what we know to be actually real.

Direct Realism is the idea that reality is directly available to us and any intermediate transformations made by our brains is not enough to change the dial.

Direct Realism has long been refuted. There are a number of examples, e.g. the hot and cold bucket; the straw in a glass; rainbows and other epiphenomena, etc.