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OK NEUROLOGISTS: You're up for a question re: Visual 'Phantom Limb' phenomina

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RJHayward:
Been seeing these visual 'side effects' or mild illusions, since I was a kid... What are those vague shadow shapes, that often will move in near synchronous, with my hand motions?
   Eyes closed, with hand behind a board, or placed under the table, it's as if an X-ray vision lets me 'see', in a crude cartoonist sense, an approximate view (actual hand is often displaced a lot from the 'shadowy' view.

   It reminded me, of descriptions of 'PHANTOM LIMB', where a person has a sense and feeling, in a limb that was injured / removed. So the theory here, is that an effect, while concealing (the waving hand / arm) is somehow producing a likeness, of the limb and motion, in a crude approximation to what the actual scene looks like.

   In my picture, I placed an ordinary sock, to show, approx, how this 'looks', keeping in mind that the eyes are closed, hand would be under a table or behind something. Of course, this is not an actual shadow of my hand, and no bright lights are there creating shadows...
   I just think that 'Visual Phantom Limb' is a pretty good explanation, especially with no alcohol use or mental illness (girlfriend might argue that).
I spoke with one Optometrist, briefly, who tended to agree, I don't have the (medical) expertise to explain / interpret that ( harmless) visual experience!

DrG:

--- Quote from: RJHayward on June 07, 2021, 09:36:02 am ---Been seeing these visual 'side effects' or mild illusions, since I was a kid... What are those vague shadow shapes, that often will move in near synchronous, with my hand motions?
   Eyes closed, with hand behind a board, or placed under the table, it's as if an X-ray vision lets me 'see', in a crude cartoonist sense, an approximate view (actual hand is often displaced a lot from the 'shadowy' view.

   It reminded me, of descriptions of 'PHANTOM LIMB', where a person has a sense and feeling, in a limb that was injured / removed. So the theory here, is that an effect, while concealing (the waving hand / arm) is somehow producing a likeness, of the limb and motion, in a crude approximation to what the actual scene looks like.

   In my picture, I placed an ordinary sock, to show, approx, how this 'looks', keeping in mind that the eyes are closed, hand would be under a table or behind something. Of course, this is not an actual shadow of my hand, and no bright lights are there creating shadows...
   I just think that 'Visual Phantom Limb' is a pretty good explanation, especially with no alcohol use or mental illness (girlfriend might argue that).
I spoke with one Optometrist, briefly, who tended to agree, I don't have the (medical) expertise to explain / interpret that ( harmless) visual experience!

--- End quote ---

It is not clear to me and I am not a Neurologist, but....

"Been seeing these visual 'side effects' or mild illusions, since I was a kid... What are those vague shadow shapes, that often will move in near synchronous, with my hand motions?"

What you are describing above sounds like Illusory palinopsia https://en.wikipedia.org/wiki/Illusory_palinopsia - something like a brief after image that is following the motion. Note that it can be idiopathic.

If you're describing seeing something like that (an image) when moving your hand behind an opaque barrier is something else and I am not really sure what you are talking about. There is a known "touch" illusion that is sometimes called the magnetic touch illusion in which you experience  some kind of tactile input because of visual information that "creates" an expectation" - https://www.sciencedirect.com/science/article/pii/S0010027716301512 and https://www.researchgate.net/publication/309039503_Commentary_The_magnetic_touch_illusion_A_perceptual_correlate_of_visuo-tactile_integration_in_peripersonal_space

The phenomenon is roughly illustrated in this video


Phantom limb phenomena are not directly related in my opinion, but may have some common characteristics in the sense of some kind of "neuronal expectation" leading to the perception phenomena, i.e., there is real neural activity produced as though it originated in the phantom limb. https://en.wikipedia.org/wiki/Phantom_limb

BTW: The technology of the nervous system, when undamaged, is never "dodgy technology" (Re: this sub-forum) - it is imperfect, but, for what it is designed to do, the programming is much better than anything else I know about. :)

RJHayward:
Thank you, Dr G. for your summaries.
   There is more info, but as an EE with very little medical / biological expertise it can be a challenge.
Seemingly unrelated, is (my) study of AI and image recognition, but it looks, more and more, like the medical and neurological sciences have much much more to offer. So I've been trying to do some more study, including basic engineering subjects, like matrix math and convolution. (The FSD or fully self driving Tesla system has a great video coverage, see the ',General Chat thread).

  Another human visual related aspect involves pulse propagation networks, having large arrays of 'sensitive' gates. Thanks again, DrG for some of that terminology used, regarding normal/abnormal situations in neurology.
   AND, (LOL), now I can, at least spell 'phenomena' now.
   Us engineers: we need the input from neurologists and other functional bio-sciences, if to make some decent progress in the future!

RJHayward:
So, I have posted under 'dodgy topic' due to the appearance, initially, of straying from purely electronics related, while vision related topics and neurology science seems, to me, to be more accurately described as 'PULSE OPERATED' systems study. That leaves enough wiggle room, to widen the subject/topic.

   Consider this 'system':
Suppose you take a big shallow box, full of set mouse-traps, each having a ping pong ball set on top. Now, this classic demo will have a predictable result; if a single ball is dropped down into the box having 50 set mouse traps, some sort of chaos will occur, a chain reaction will propagate thru, untill all or most traps have sprung.
   For that demo system, you could 'tune' your response, for example you could set up just barely enough (set traps w ball) so that the chain reaction just barely catches, (or just stops early).
   Believe it or not, these sorts of 'impulse' reaction systems have commonality with vision and retina response.
   Here are some questions coming up regarding pulse response arrays, and the hand movement results I am getting:
  For the coordinated motion, I could imagine doing experiments, measuring nerve signals in the hand. However, making (nerve electric) measurements of eye and retina activity is a bit obscure! Plus, those perceptions of activity might not even involve the eye directly, so any experiment to measure these movements or illusory perception, well, that sort of testing is way beyond my skill set.
But if you could, the idea is to try to corelate hand movement, direction of motion etc with the perception (leaving the subject's personal interpretation out of it).
  Now, as to any 'mapping', there seems to be lots of rotational translations, where a linear movement causes a response (in this hypothetical experiment setup) where subsequent pulse movement or migration of pulse groups, becomes mapped into a rotation progress, rather than simple straight line paths.
Sorry to be, maybe, too obscure, but mainly questions about vision and use of pulse response in a matrix (of mapped gates).
...more later, thanks

DrG:
I'm not sure what you are after. It sounds like you want to be able to measure a neuronal correlate for the afterimage you experience when you wave your hand. Is that close?

I also do not understand exactly what is meant by "pulse response arrays". I did search and saw a bunch of hits - radar and other things and I just don't have a good feel for that. Pulse propagation networks is a very old neural network model/concept https://www.brainfacts.org/thinking-sensing-and-behaving/vision/2012/vision-processing-information that I vaguely recall.

I admire your willingness to think about the issues and to ask questions, but there is a lot of background to understand before you can, even mentally, devise experiments that would make sense. Here is the deal bluntly and I really hope you are not offended because I mean no offense.

I feel like I have been down this road many times with many "EEs". That may be unfair stereotyping on my part, but the typical EE curricula for a 4 year degree likely does not include much physiology, sensation and perception, learning theory, or general neurobiology or neuroscience. Yet all of that is terribly important to having a foundation to even grasp at a speculation. To be sure, I have known some very sharp biomedical engineers with advanced degrees and who have studied these topics in depth - it is not out of the realm of engineers (or anybody else), I am not saying that at all. I am saying that it is specialized and it is complicated and it looks like we don't yet know as much as we don't know.

I have been annoyed for years that a group co-opted neuronal terminology and have given us the new and improved "deep learning" (aka classifying things). I know something about neurons, not everything, but something about them, and I say that those ain't neurons and I don't see the value in sharing the terminology to suggest that they are neurons. I may be a bit biased :)

A typical (and terribly frustrating)  level of understanding of how we "see" starts and functionally stops, at light hitting the retina. I am telling you that you do not need any light hitting a retina to report "seeing". This has been demonstrated often. You "see" while dreaming but your eyes are closed. Some musicians "see" the color of music - no relevant retinal information is needed. Hallucinogenic drugs are named as such for a reason. I promise you that I (well someone) could stick some electrodes in your brain and get you to "see".

Look at the typical mickey-mouse diagram of the visual system: [https://www.brainfacts.org/thinking-sensing-and-behaving/vision/2012/vision-processing-information]



Where do you think "seeing" is located in that diagram?

In fact, I would argue that no two people could EVER see the same thing - it is impossible because 1) they can't occupy the same space and 2), which is much more important, no two people have exactly the same genetic+developmental+experiential makeup that could possibly lead to an identically functioning visual cortex (and other parts). One typical problem is that folks want to concentrate on the transducer (eye) because it is so much simpler than the rest, but that does not mean that the retina is the most important part.

I saw this the other day (I can't remember where or I would give the cite, my apologies to the author) and, apart from ignoring the inconvenient bit about "all things being equal", I thought it was so funny that I saved a copy.



So, I probably can't be of much help because I don't understand what you trying to do, but again, no offense intended. Hopefully, I have been, at least, mildly entertaining :)

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