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A human can sleep with one or both eyes open, but as far as I know it's not at all related to brain activity. The person's brain is still fully asleep. See: h

A human can sleep with one or both eyes open, but as far as I know it's not at all related to brain activity. The person's brain is still fully asleep. See: https://en.wikipedia.org/wiki/Lagophthalmos#Nocturnal https://en.wikipedia.org/wiki/Lagophthalmos#Nocturnal

sp332 10y ago
Your brain can still react to things when it's asleep though. You can be shaken awake, or shouted awake, or woken up by a bright light. It doesn't seem impossible that seeing something dangerous while asleep could wake you up.
- Mz 10y ago
  Presumably this is exactly why my father learned to sleep with his eyes open while caught behind enemy lines in Vietnam for, as I understand it, a month or more.
david-given 10y ago
I remember once waking up, when, for some reason, I had my eyes open. It was weird: all I saw was just shape; not shapes of anything in particular, but just pure essence of what shape really was. Then, over a period of a few seconds, and in distinct chunks, it suddenly resolved into things I could actually identify, and I realise what I was looking at. After the fact I put this down as the pattern-matching areas of my brain starting working rather more slowly than the rest of my visual cortex, so it took a while before they starting resolving what my eyes were seeing into meaningful concepts. I have a variety of mild sleep disorders. I can recommend them as a hobby; they're fascinating. Admittedly, it helps that being hag-ridden is so familiar it's practically an old friend; the first few times were utterly terrifying[ * ]. But the weirdest of the lot is something I've dubbed false memory syndrome, where I'll remember something, while quite conscious, which never happened, and frequently in quite some detail. Just last night I had apparently written and drawn a comic book. That was better than the time I was on the run after having killed someone... [ * ] Apparently there's a theory that this is where alien abduction myths come from.
- trentmb 10y ago
  > It was weird: all I saw was just shape; not shapes of anything in particular, but just pure essence of what shape really was. Wonder if that's what it's like for a newborn. https://en.wikipedia.org/wiki/Molyneux%27s_problem https://en.wikipedia.org/wiki/Molyneux%27s_problem
  - pbhjpbhj 10y ago
    There is some conjecture that babies have synesthesia too - so it would be a case of visually receiving sense shape imagery and the brain interpreting that as colours, forms, tastes, pressure, warmth, scents, and such too. Now that seems like enough to make you scream and seek solace in innate behaviours.
- animal531 10y ago
  Yeah, that first part happens when you on occasion mentally wake up faster than your body does, which is then still sleep paralysed. It can be pretty scary the first time, as it feels as if there are shapes (ie. humanoids) lurking around you. Also when you try to move your brain remembers and plays the motion as if it's happening, but you're still paralysed so you keep resetting back to whatever position you're lying it. The same probably holds true for sight.

sp332 10y ago

Your brain can still react to things when it's asleep though. You can be shaken awake, or shouted awake, or woken up by a bright light. It doesn't seem impossible that seeing something dangerous while asleep could wake you up.

Mz 10y ago
Presumably this is exactly why my father learned to sleep with his eyes open while caught behind enemy lines in Vietnam for, as I understand it, a month or more.

david-given 10y ago

I remember once waking up, when, for some reason, I had my eyes open. It was weird: all I saw was just shape; not shapes of anything in particular, but just pure essence of what shape really was. Then, over a period of a few seconds, and in distinct chunks, it suddenly resolved into things I could actually identify, and I realise what I was looking at. After the fact I put this down as the pattern-matching areas of my brain starting working rather more slowly than the rest of my visual cortex, so it took a while before they starting resolving what my eyes were seeing into meaningful concepts. I have a variety of mild sleep disorders. I can recommend them as a hobby; they're fascinating. Admittedly, it helps that being hag-ridden is so familiar it's practically an old friend; the first few times were utterly terrifying[ * ]. But the weirdest of the lot is something I've dubbed false memory syndrome, where I'll remember something, while quite conscious, which never happened, and frequently in quite some detail. Just last night I had apparently written and drawn a comic book. That was better than the time I was on the run after having killed someone... [ * ] Apparently there's a theory that this is where alien abduction myths come from.

trentmb 10y ago
> It was weird: all I saw was just shape; not shapes of anything in particular, but just pure essence of what shape really was. Wonder if that's what it's like for a newborn. https://en.wikipedia.org/wiki/Molyneux%27s_problem https://en.wikipedia.org/wiki/Molyneux%27s_problem
- pbhjpbhj 10y ago
  There is some conjecture that babies have synesthesia too - so it would be a case of visually receiving sense shape imagery and the brain interpreting that as colours, forms, tastes, pressure, warmth, scents, and such too. Now that seems like enough to make you scream and seek solace in innate behaviours.
animal531 10y ago
Yeah, that first part happens when you on occasion mentally wake up faster than your body does, which is then still sleep paralysed. It can be pretty scary the first time, as it feels as if there are shapes (ie. humanoids) lurking around you. Also when you try to move your brain remembers and plays the motion as if it's happening, but you're still paralysed so you keep resetting back to whatever position you're lying it. The same probably holds true for sight.