Sat down to dinner, for me primarily a bowl of noodles made by my father-in-law. I reach into the bowl with the chopsticks and pull out some noodles and I stop - do the noodles have a textile-grid pattern impressed into their surface? How did he do that? No - no, there's no such texture there, the noodle's surface is smooth..
I blink - again, I see a screen texture there, as though on the surface of the noodles, but when I look for the features supporting that pattern - local changes in brightness, depth, something - it's not there, what I see is consistent with a smooth noodle surface, and the feeling of seeing a fine grid pattern vanish.
I look away, thinking this is an afterimage - is it from the thin bamboo blinds on the windows, with the sun setting outside? No, it's not the right pattern.. is there a cloth nearby, with the grid pattern? Nothing I can find. I haven't looked at a screen..
It repeats a few more times. Also during dinner, looking at some sliced sandwich pickles (from leftover barbecue lunch) - sliced with that wavy sinusoidal pattern - I get a weird feeling that the pickles don't actually have that texture, that they are flat and the sinusoidal pattern is a shadow. It was a confusing percept.
Anyways - I think what was happening here was another case of what I have named gardener's hallucinosis, though I had not been gardening. But there are a couple of related factors: with the gardening episode, I had been outside all day - gardening - with a minor alcoholic drink (a beer) in the afternoon. Today, I had been outside all day - hiking and at a festival - with a beer in the afternoon.
Also, this morning I awoke early, about 6am, with the worst headache I've had in ages. I took an ibuprofen, which usually does the trick, and tried to sleep again for half an hour but it had no obvious effect. Then I gave up and went downstairs, took a tylenol and drank a pot of coffee. That fixed the headache for the most part, though I did have (and still have, now, 14 hrs later) a sore ophthalmic nerve above my right eye (always a sure sign of migraine for me).
At the time of the gardening episode, I don't think I recorded any significant headaches, though in retrospect I know I had often been waking up - when we lived in that yellow house - in the middle of the night, seeing Kluver-webs in front of my eyes. So maybe I was in a sub-migraineal state?
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Thoughts about the phenomenon. It was interesting how the grid-impression vanished when I investigated it. It definitely felt there in a spatial sense, I felt it as a grid of lines, much like a fine window screen, there on the surface of the noodles. But when I "gave it a second thought", looking for evidence for what I thought I was seeing, the percept reverted to the veridical. The weirdness here, I suppose, was some kind of stable state of unwarranted activity in extrastriate cortex, but when I directed attention to cortex where the input for detection of such feature elements should have been, it was enough to "correct" the unwarranted activity. Which, weirdly enough, then snuck back into the unwarranted state once I stopped attending.
Should also note that while with the gardening episode I had been intensively visually investigating the features that I later hallucinated, in this case I can't think of why I was seeing the particular patterns I was seeing. It is possible that I had glanced at some pattern and just failed to figure it out in the moment. But it wasn't a repetitive, intensive 'training' like with the gardener's hallucinosis.
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Migraine post!
