I'll offer a personal experience (that I've described on HN before) that is more or less related. I have a history of migraine. One commonly-reported symptom o

I'll offer a personal experience (that I've described on HN before) that is more or less related. I have a history of migraine. One commonly-reported symptom of migraine--one that I also experience--is "scotoma": a vivid moving visual hallucination that obscures a large portion of the visual field. I discovered a few years ago that I could read books that I couldn't see because of scotoma. The details of my scotoma have changed over the years. In my late teens and early twenties they tended to be large, whirling pinwheels of light occupying about half my visual field, usually off-center to the lower left. In recent years they've moved around a little and more closely resemble vivid, shining triangular prisms with iridescent zebra stripes scrolling over and radiating from the surfaces. Whatever their shape, they're extremely vivid--generally much more vivid than anything in the real world. They're also distracting, and when they occur, I can't see anything past them at all, except around the edges of my visual field where they don't appear. That's maybe less helpful than it might be, since the scotoma moves with my eyeballs, so I can't look around it effectively. I discovered the peculiar interaction with reading one day when I was reading a book that I found engrossing tell-tale symptoms alerted me that a migraine with scotoma was incoming. I was vexed because I didn't want to stop reading, and I resolved to just continue until I couldn't read anymore. That point never came. The scotoma blossomed into its full glory, a vivid, scintillating prism that obscured most of the center of my visual field. I couldn't see the book at all, nor the hand holding it. I could still read, though. I became preoccupied by the unexpected phenomenon of reading text that I couldn't see, and started reading aloud from the book. Eventually, the scotoma faded, as it always does, and I was able to confirm that what I had been reading during its effects was in fact what was actually on the page. I take my experience to mean that the process of reading and interpreting the text and the process of being subjectively aware that I'm doing it are two different processes, and it's possible for one to continue even when the other is prevented. I had always before assumed that the two processes were one and the same. It never occurred to me that they could be different until the scotoma demonstrated it to me. On another occasion I discovered another crack in my naive model of reality, when exhaustion plus a stimulant offered me the chance to be both awake and asleep at the same time, but that's another story.