Why suffer a Farington ? (Maybe because I'm a Farington, also)

[Xena E]

   XenaE I wanted to take a few secs to further explain that Perceptual Phantom Limb effect, I've coined the term.

   Photo showing, eyes closed and blocked, the retinal image, or residual background in visual system.   The effect is, when the (actual) hand is waved around, there is a 'phantom' hand-like blob, almost similar to something made out of transparent glass...
The effect 'seen' will track the real hand motions, in speed and direction, but often offset some...as long as things are still in front.
   Imagine a glass 'stick' that will do tiny distortions, in the visual image, as it passes over;  much like a moving magnifying lens might do.  That's approximately how this illusion presents itself.
   The actual hand, in the little experiment, can also be placed behind a solid wall, or plywood block or table, as long as it's physically in front.

Thanks for sharing, that is much clearer.

That certainly sounds very sixth chakra, rather than purely an altered state of perception.

I have heard of people who have such detailed persistence of vision that they have been able to negotiate obstacles with confidence after being plunged into darkness. That is different I think.

Being able to see your own heart beat isn't unusual, the optic nerves are sensitive to pressure and a brightness change in time with your pulse or even a point flash of light in the peripheral vision is common, I have that myself, its attributed to randomly occurring hypertensive events.

After a partial Parietal Lobe resection several years ago, I have kind of the opposite of phantom limb syndrome. The right side of my face 'shrinks' when I close my eyes. It only reestablishes when I open them again and my right eye gives a visual reference of its position. If I lie on my right side in bed, with my face exactly right on the pillow, I can get the spooky feeling of my right side 'disappearing'. My Neurologist pointed me at the Oliver Sacks book (another of his that is worth reading is Uncle Tungsten, an autobiography of his childhood and his relationship with his, industrial chemist, uncle).

Was that for severe epilepsy?

Co worker had this done, he has his wife shave him as he cannot safely himself. The other limitation is he cannot drive because of impared spacial awareness. It seems brutal how the operation has affected him, but the alternative was going to be life limiting, he says bumping into a few door frames is a small price to pay.

[Gyro]

Was that for severe epilepsy?

Co worker had this done, he has his wife shave him as he cannot safely himself. The other limitation is he cannot drive because of impared spacial awareness. It seems brutal how the operation has affected him, but the alternative was going to be life limiting, he says bumping into a few door frames is a small price to pay.

Brain tumor (which is still being surprisingly well behaved), but it did first manifest as painful sensory seizures. Mine mainly causes sensory deficit, In fact I was able to get my license back after 5 years (subject to frequent reviews). Right Parietal issues tend to cause left side neglect, where the mind tends not to notice stuff on the left side (including the face, shaving etc.). Strangely the left Parietal tends not to do the same thing, but is still subject to sensory conflicts - something to do with typically being the dominant hemisphere. Interesting stuff when you get into it - for instance, for a few months after surgery, every time a bird flew past I was absolutely convinced that somebody was throwing frisbees at me and would duck!

P.S. The fun bit... having it done awake.

[RJSV]

   Wow, thanks Gyro, that's a whole load of stress, added to all the more regular hassles.
Reminds me, that many doctors have a cultivated sense of responsibilities, and so just the act of bringing something up, some curious medical situation, always causes (the doctor) to feel obligated to respond, and 'solve' the issue.
So, while a patient might simply have some curiosity, rather than some 'demand' for cure, you have to, somehow, get him/or her to relax.
In older times, one might cross legs, on the exam table, break out a pack of cigarettes, and say some chit-chat thing;
   "HEY DOC;  (I noticed some weird facial things...)".
   But seems like today's busy doctor hasn't time, for patient's technical curiousity.   Hmmm.
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   Now, today, I've a related Calculus problem, question:
   As shown in attached diagram, having a 'sweep', similar to old radar screens, a sweeping line that is measuring the light intensity, will produce a waveform...obviously only a positive number, intensity, and then using that, to generate a First Derivative, or slope of the intensity at one particular arc.
Of course, I made the skew rate reasonable, by blurring each object slightly.   But then I've realized, that slope, or first derivative of intensity will have negative values and positive.   So that's a little weird, unexpected.   I can do the math, blindly, (no intended pun), but real world light intensity, at least, has no negative values.

   Just a curiousity...no need to fix anything..

Please see enclosed diagram, of sweep across an image.   Thanks.

[T3sl4co1l]

Well units of derivative aren't the units of the thing, it's thing per rate (in this case, per distance or angle of sweep). Whether the reverse is true (integral is a positive-definite function) depends on where you start, or for the indefinite integral case, what the constant of integration is.

Tim

[Xena E]

Was that for severe epilepsy?

Co worker had this done, he has his wife shave him as he cannot safely himself. The other limitation is he cannot drive because of impared spacial awareness. It seems brutal how the operation has affected him, but the alternative was going to be life limiting, he says bumping into a few door frames is a small price to pay.

Brain tumor (which is still being surprisingly well behaved)...

That's a bummer... I'm sorry to hear that ...but they don't do the procedure for cosmetic reasons, long may it remain well behaved...

but it did first manifest as painful sensory seizures. Mine mainly causes sensory deficit, In fact I was able to get my license back after 5 years (subject to frequent reviews). Right Parietal issues tend to cause left side neglect, where the mind tends not to notice stuff on the left side (including the face, shaving etc.). Strangely the left Parietal tends not to do the same thing, but is still subject to sensory conflicts - something to do with typically being the dominant hemisphere. Interesting stuff when you get into it - for instance, for a few months after surgery, every time a bird flew past I was absolutely convinced that somebody was throwing frisbees at me and would duck!

P.S. The fun bit... having it done awake.

AWAKE! I suppose the surgeon needs to know when they're going to far off piste, digging around in there.

X

[Gyro]

That's a bummer... I'm sorry to hear that ...but they don't do the procedure for cosmetic reasons, long may it remain well behaved...

Thanks Xena. Yes, it was a case (like your co worker) where I was having so many seizures that I was going into 'status', seriously life limiting! Both outcomes are life limiting but it's being so well behaved, it's all getting a bit embarrassing!

AWAKE! I suppose the surgeon needs to know when they're going to far off piste, digging around in there.

Exactly that, there are a couple of centers in the UK (probably more now) pioneering awake brain surgery, Southampton being one of them (being in the UK, you might have seen one of the documentaries*). It took me from a surgeon saying 'In my opinion it's inoperable, it's too close to eloquent areas, speech etc.' to 'lets open your skull, get a decent biopsy (the previous burr hole one was unsuccessful due to an image mapping problem) and take a closer look'.

As the forum readership is so wide, I might take the opportunity to quickly talk about the awake bit as there could be someone out there is facing the same situation. Yes, it's a daunting prospect up front, but there really is nothing to fear. The brain is completely insensitive to pain, the only bit that isn't is the scalp and they pump that full of local anesthetic, you get a few bone type noises but completely painless. For an engineer, the whole process switches between incredibly interesting (stimulation and surface mapping the brain areas, inducing speech arrest etc.) to very boring... 'if you ask me to name that f*** yellow plastic comb and pen one more time...!', while enviously eyeing other more exciting objects on the next shelf down. There's still a particularly skilled anesthetist (a very tight theater team who always work together), you have a line in so he can have you asleep in seconds if things turn unpleasant. For me it meant that he managed to get about 90% out (with an infiltrating tumor there is no clear boundary), so it let him really push the limits as far as possible without causing unnecessary deficit - compare that to waking up after a general anesthetic to find that this or that doesn't work anymore or the disappointment of hearing that they took a 'conservative' approach on % removal. The text books confidently label all the area functions, the surgeons are constantly finding that everyone is a bit different - awake is pushing that knowledge and identifying new pathways a lot!

Recovery time is way shorter too, general anesthetics extend it massively. My surgeon is advocating for day case brain surgery! In early, surgery by mid morning, a CT after lunch to check for unexpected bleeds and then off home late afternoon, carefully monitored and emergency help number of course. In my case, I was home after 2 days, "How are you feeling, no seizures? Ok lets get you home before you catch something". You really don't want a hospital acquired infection when you've had your Dura opened! Recovery in your home and bed is so much better.

I don't know, maybe it will help somebody out there at a difficult time. If not, then apologies for the OT.


Edit: * Damn, not currently available... https://www.channel4.com/programmes/brain-surgeons-between-life-and-death Maybe YT somewhere.

[AVGresponding]

I have heard of people who have such detailed persistence of vision that they have been able to negotiate obstacles with confidence after being plunged into darkness. That is different I think.

Yes, this is more a spatial awareness thing, and is something that can be practiced and improved upon.