Science Questions

Why do I see things as I go to sleep?

Tue, 3rd Sep 2013

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Connor from Tillingham asked:

One night when my wife and I were getting ready to go to bed and we turned off the light, I closed my eyes, and suddenly I saw an image of an old fashioned bakery. Could this be related to my memory?


Chris - Well, this is actually a sort of hallucination which is caused by often,

Old Fashioned Bakery

putting people into the dark. Ginny can probably comment on this in a second, but there are these things which are called float chambers and you put people in these experiences on purpose sometimes to do research studies. You effectively put someone in a very quiet, very calm, dark environment. Itís a sensory deprivation experience and this has the effect of triggering all kinds of strange hallucinations. They do it with medical students sometimes in psychology studies and people will say, ďI can hear voicesĒ ďI'm convinced the telephone is ringingĒ ďI'm seeing thingsĒ. And itís probably because in the same way as we were discussing earlier, when you have a tinnitus, this is the hearing part of the brain, failing to get a signal from the earís cochlea, so it turns up or amplifies the signal a bit. And up comes the noise, the hiss, which is what you end up hearing as tinnitus. It seems like when you deprive the visual system of inputs and other parts of the brain, they start to invent signals or increase the amplitude of signals that are already there at low level and it makes them manifest a very real experience. Would you go along with that, Ginny?

Ginny - Yeah, I think that sounds right. I mean, our brains are quite incredible things and we donít fully understand them yet. One of the things we think is that we actually store more memories than we know we do. Actually, when we forget things, itís not that the information isnít there anymore. Itís often just that we are unable to access it. So it maybe that this was a memory that you donít even know that you have, but thatís there. And because it was dark and it was quiet, it came back to you.

Chris - Exactly and so, it was sort of playing out in the visual system, just because that part of the brain is already sort of seeing that experience.

Dave - I guess the other effect is certainly I get sometimes as I go to sleep, I start seeing random images and if you're kind of getting to bed and turning lights out, it might be something related to sort of starting to dream while still being awake.

Chris - Thatís certainly true. It could be sort of that weird phase between being awake and being asleep. You do have rather strange experiences. They're called hypnagogic experiences, aren't they?

Ginny - Yeah. There are even some people who can have lucid dreams where you can sort of control your dreaming and itís almost like you're awake, but you're dreaming, but you're asleep and we donít fully understand how they do it. But it could be something on those lines.


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