Crepuscular Hallucinations

April 19, 2021 6:21 PM

Going on 20 years or so I've experienced occasional, for want of a better word, visual hallucinations. I know they're not real (except perhaps in one case) and I'm not worried about them in the least. I just want to know if they're common and if there's a name for them.

They typically occur in the complete dark while my eyes are accommodating from light after having got up to go to the bathroom. For instance, in the complete dark, with closed eyes and with a cover over my face I can sometimes "see" my hand very dimly. If I put up two fingers I see two fingers. If I move my hand I can see it move. I know there are many inputs to the visual system, including very detailed information about the body map. What I think is happening is that my visual system is using that information to tell me what it knows in other ways.

Relatedly, perhaps, are visual phenomena that happen in dim light, also usually after having just been exposed to brighter light... and with my eyes closed. In a few cases I seemed to be seeing the red blood cells coursing through my retinal capillaries. I can just believe that my eyes were sensitized so that they were able to see what was going on in the retina directly. So this case is the one that I think might not be a hallucination, as such. But perhaps it was after all.

And sometimes, very rarely, again in crepuscular situations, I can see moving figures along a horizontal line at or below the center. Sometimes they are abstract and sometimes they suggest figures of sorts. I would even say they are similar to the descriptions I've read about the "machine elves" people see when taking DMT (FWIW, I have no direct experience of this). I assume this is a case where my brain's image recognition apparatus is primed to identify figures from noise much as "deep dream" does. To be clear I was not in any kind of partial dream state; I was fully awake.

Again, this isn't something that alarms me and if I weren't such a nerd I'd neither have noticed it or thought much about it. And the images are generally dim, though sometimes distinct. Anyway, I'm wondering if anyone else has noticed/experienced this and, better, if someone can point me for a name for this (these) phenomena and anything written about it; I'm going to tag this as a "science and nature" question.

posted by sjswitzer to Science & Nature (23 answers total)

Images, or afterimages?
posted by Rash at 6:32 PM on April 19, 2021 [1 favorite]

Response by poster: I know about afterimages and it's definitely not them. For instance, the things that I see actually move.

And to be clear, I know about moving afterimages like the afterimages of a rotating spiral and it's definitely not that either. These images move organically and in some cases (like when I move my hand) in response to things that happen afterward.
posted by sjswitzer at 6:43 PM on April 19, 2021 [1 favorite]

Two ideas that spring to mind: firstly, the human brain produces DMT and it's possible that at those moments you're experiencing a peak of production. I don't know of any specific research on this though. Secondly, your description of seeing figures sounds like pareidolia, which refers to the fact that the human perception system is wired to find faces and figures in the visual input, and this sometimes triggers "false positives".
posted by nomis at 7:10 PM on April 19, 2021 [1 favorite]

Seconding pareidolia. Everything we perceive with our eyes is actually a best guess our brains are making at what is before us based on what limited information our eyes (or other sources of info, like proprioception, as you mention) can give us at that moment. In a near-dark situation, it's going to fill in more details, accurate or not, which prioritize certain patterns. Often these are human figures or faces since that's the sort of pattern our brain loves so much.
posted by subocoyne at 7:28 PM on April 19, 2021 [1 favorite]

In case it helps, something sort of like this happens to me when I'm waking up but still half-asleep. My eyes will be closed but I will "see" the room as I expect it to be.
posted by aniola at 7:47 PM on April 19, 2021 [1 favorite]

Could it be phosphenes?
posted by zoetrope at 7:48 PM on April 19, 2021 [1 favorite]

Response by poster: Aniola, I have experienced that as well. It definitely seems related.
posted by sjswitzer at 8:02 PM on April 19, 2021

Response by poster: I don’t want to threadsit this but I will say that pareidolia definitely seems relevant! It’s my main theory. Still, it seems a bit broad to explain my particular experiences.

I’ll try to sit back and see if anyone else has related experiences.
posted by sjswitzer at 8:10 PM on April 19, 2021

Response by poster: Thanks to the MeFi magic of related questions I found this answer that seems very close to what I was asking.
posted by sjswitzer at 8:23 PM on April 19, 2021

Not sure how it helps one way or the other, but this reminded me of instructions about astral projection / lucid dreaming. Get into a relaxed space where you can start to see through your eyelids, and then project yourself into that space. I can't say I've ever astrally projected, but I have used this to enter a lucid dreaming state where I was conscious and also dreaming. Which is really fun to go along with your experimental premise.
posted by indexy at 8:31 PM on April 19, 2021 [3 favorites]

I’ve experienced level 4 closed-eye visualizations as linked in your linked comment from a related question. It tends to happen when I’m way over-tired and finally able to go to sleep—it’s like I start dreaming before my brain gets down to the REM state. I see constantly shifting cartoonish pictures, often of clearly defined faces—not just random shapes with pareidolia applied. It’s like watching a cartoon projected on the inside of my eyelids. And for me it’s kind of scary, because who knows what weird shit my brain is going to conjure up in this liminal state. I have on occasion woken myself up from this state because it was too intense.
posted by ejs at 8:48 PM on April 19, 2021 [3 favorites]

Hypnagogia
posted by ShooBoo at 8:48 PM on April 19, 2021 [2 favorites]

Yep, seems you found a few good things. I was gonna say that I do all of the things you mention and have relatively "that's not weird and I do the same and I have an explanation". And I've done my fair share of psychedelics in my past. You can totally see your blood cells in your eyes if you look just right. You can also see the changes in blood flow and really tiny activations. It's said that astronauts occasionally see a flash from a single gamma ray or such hitting the retina. Out eyes are weird.

The best time for such things is like when you wake up and should get out of bed but try to stay in for whatever reason but can't really sleep and you just hover around that awake/asleep point... Oh the things you'll see.

TL;DR, not weird, don't think there's a name that encompasses them all into one thing.
posted by zengargoyle at 9:02 PM on April 19, 2021 [1 favorite]

Response by poster: I think that “closed-eye hallucination” is the answer to my main question. Thanks too for confirmation that I might have actually seen my retinal capillaries.

But I’m still quite fascinated by this and very interested in people with similar stories.
posted by sjswitzer at 9:12 PM on April 19, 2021

I'm not sure I can warp blue field entoptic phenomenon:

The blue field entoptic phenomenon is an entoptic phenomenon characterized by the appearance of tiny bright dots (nicknamed blue-sky sprites) moving quickly along squiggly lines in the visual field, especially when looking into bright blue light such as the sky.[1] The dots are short-lived, visible for a second or less, and traveling short distances along seemingly random, curvy paths. Some of them follow the same path as predecessors. The dots may be elongated along the path like tiny worms. The speed of the dots varies in sync with the pulse; they briefly accelerate at each heartbeat.[2] The dots appear in the central field of view, within 15 degrees from the fixation point.[3] The left and right eye see different dots; someone looking with both eyes sees a mixture.

Most people are able to see this phenomenon in the sky, although it is rather weak, and many people do not notice it until asked to pay attention. The dots are highly conspicuous against a monochromatic blue background (~430 nm) instead of the sky. The phenomenon is also known as Scheerer's phenomenon after the German ophthalmologist Richard Scheerer, who first drew clinical attention to it in 1924.[4]

Explanation

The dots are white blood cells moving in the capillaries in front of the retina of the eye.[5] Blue light (optimal wavelength: 430 nm) is absorbed by the red blood cells that fill the capillaries. The eye and brain "edit out" the shadow lines of the capillaries, partially by dark adaptation of the photoreceptors lying beneath the capillaries. The white blood cells, which are larger than red blood cells, but much rarer and do not absorb blue light, create gaps in the blood column, and these gaps appear as bright dots. The gaps are elongated because a spherical white blood cell is too wide for the capillary. Red blood cells pile up behind the white blood cell, showing up like a dark tail.[6] This behavior of the blood cells in the capillaries of the retina has been directly observed in human subjects by adaptive optics scanning laser ophthalmoscopy, a real time imaging technique for examining retinal blood flow.[7] The dots will not appear at the very center of the visual field, because there are no blood vessels in the foveal avascular zone.

into a mechanism which accounts for your impression that you are seeing "red blood cells coursing through my retinal capillaries", in dimmer light after exposure to brighter light -- perhaps something like the parts of your retina which were in shadows of capillaries not showing up in the afterimage of the bright light. so that they paradoxically appear as dark squiggles in the afterimage, and the white blood cells letting enough of the dim light through to give a sensation of light moving along the dark squiggles (this explanation doesn't work for closed eyes unless enough light is getting through your closed lids, though), but I'm morally all but certain they are closely related.
posted by jamjam at 12:03 AM on April 20, 2021 [1 favorite]

In her last years, my mother nearly blind with macular degeneration started to experience Charles Bonnet Syndrome “ . . .the old chap in the portrait over the side-board – he’s now wearing a flowered garland . . . and there’s a sailor with a hairy leg swimming in the sea beside your father’s last command . . .” It seems to be the visual cortex desperately trying to make sense of random jangling of the optic nerve.
posted by BobTheScientist at 12:54 AM on April 20, 2021 [1 favorite]

I get all of the ones you described, too. My brain likes to file the moving figures on or below the horizontal as “cats,” but I think that’s just because I’m used to actual cats on or below the horizontal. The hand one in particular has always intrigued me, especially after I read The Wonderful Story of Henry Sugar as a kid.

FWIW, I used to do a whole lot of psychedelics, but I actually think I got more of these closed-eye phenomena (plus some others you didn’t describe) before I ever did drugs than I do now (three years sober). Brains are weird and cool.
posted by cabbage raccoon at 3:03 AM on April 20, 2021 [2 favorites]

I think you've gotten your answer, but I experience these when I'm having migraine aura. They seem to be related to whatever ambient light there is showing through my closed eyelids, and can feel distressing. I get relief by blindfolding myself.
posted by Orlop at 7:02 AM on April 20, 2021 [1 favorite]

Seeing your hand with your eyes closed is, as you suspected, a body awareness thing. Specifically, proprioception. This technique of 'seeing' ones hand is used in many disciplines to anchor the mind into an altered state, including hypnosis, lucid dreaming, and during sessions with a light and sound machine.
posted by ananci at 7:53 AM on April 20, 2021 [1 favorite]

Response by poster: jamjam, the blue field entoptic phenomenon has jogged my memory... it was a long time ago.

I saw the alleged red blood cells after entering the bathroom in the dark, turning on the light and then closing my eyes immediately because it was so bright. The light filtered through my lids as a red glow against which the red blood cells appeared as darker shadows. If you can see white blood cells under one set of conditions it seems at least plausible you can see red blood cells under others. I remember seeing them course single-file through a capillary-like network. I've managed to reproduce it maybe one more time but not recently.

I'll see if I can experience the blue field entoptic phenomenon but I have enough floaters that it may be difficult.

Thanks, everybody! There's a lot of fascinating information in the replies.
posted by sjswitzer at 10:39 AM on April 20, 2021 [1 favorite]

Response by poster: Nice patch of clear blue sky here today and I can report back that I did indeed see the blue field entoptic phenomenon! If I ever noticed it before I might have confused it with floaters (though floaters appear as dark splotches—also blood cells, I believe—and these are bright speckles. (Happy too that my floaters aren’t so bad after all.)
posted by sjswitzer at 10:53 AM on April 20, 2021

As a side note, if you're interested in exploring more of these phenomena, look into the Ganzfield effect. The undifferentiated white field of the goggles (which you can make yourself) will quickly result in interesting visual experiences, including full hallucinations. It's fascinating to see how our visual cortex processes information, or a lack thereof.
posted by ananci at 11:19 AM on April 20, 2021 [1 favorite]

I think you might enjoy Oliver Sacks book Hallucinations. It is so interesting and i am always touched by how lovingly he portrays the people whose experiences he describes.
posted by 15L06 at 3:22 PM on April 20, 2021 [1 favorite]