I don't understand this obsession with the "purpose" of dreaming. As far as I have experienced its just noise on the wire that we sometimes are conscious enough to recognize.
Having spent enough time in extremely sleep-deprived states for projects recently, I've experienced firsthand a lot of funky stuff going on (e.g. falling asleep and waking up with a full page of class notes in front of me, or realizing that I've started 'dreaming' while editing a document, the dream being seeded by the words I was processing.)
I have lucid dreams almost every night now. I'm talking about entire story arcs with plot twists.
Last nights had Donald Trump, my wife and Jennifer Love Hewitt. There were riots going on and people reading newspapers with moving video ink. There was an old book called "The Fall" that was filled with fascinating ink drawings of ritualistic acts (eg: a man sat cross legged on broken fragments of his own arms). Etc. That kind of stuff. Had a full story.
Noise on the line in Brain-space could still be the case, but if so we can learn something from that noise regarding the way brain structures work.
What I'm saying is if it is just noise, then the noise must be feeding into an entire projective area of creativity that amplifies that noise, not just locally but over time, and in ways that maintain consistency.
Consider a c struct describing a circle, with fields for position, radius, and color. Imagine you have a buffer full of random noise, and you cast it to an array of said structure. You then render the array to a screen, you'll get a bunch of randomly placed colorful circles, rather than a bunch of visual noise.
In this model a series of consecutive bytes has a predefined meaning existing outside of them (namely in the source code that defines the struct), so when they are read they are cast as a struct-circle object.
This also only works well for scalar fields, not associations (pointers in the C program's case) and more finely grained items.
Also, where would that (the definition of the "struct") happen with the brain? Is there any literature showing anything similar, that we have memory fields that pre-correspond to specific objects through some mechanism?
Besides, dreams can have very clear structure and narrative, which takes them outside the realm of what can be achieved with noise, unless the "struct" has fields that correspond to things like emotions, faces, narrative changes, etc.
You can also take other analogies. Complex systems usually have several layers of planning or decision making and if you randomize on the top layers, it will still appear to be structured, because the top layers have different degrees of freedom.
To take another example, a self-driving car might make a decision to switch the lane. If you randomize on that level, it will randomly switch, but the movement will still be smooth, because this is done one or more layers below.
We examine the circles not to learn about the data from which those circles are derived, but rather to learn about which structs and other properties are defined in the system. We might find circle struts, square structs, triangle structs, but never spheres, boxes, or pyramids. Or maybe some people (schizophrenics) have the metaphorical three dimensional structs and others do not.
Actual noise with no coherent structure is enough for the brain to start imagining patterns - can confirm that having tried it myself, with white noise in my eyes and ears for half an hour, I ended up having dream-like hallucinations while awake:
I want to say, pyramidal cell in visual cortex connectivity network decoherence - similar happens with mice after sleep deprivation, and is reminiscent of the phenomenon of HPPD, and with stochastic resonance.
Noise 'on the wire' in a neural network is going to look different from noise on an actual copper wire.
E.g. noise in the brain might be an increased incidence of errant impulses/signals. There's evidence that sleep involves pruning meaningless connections - noise in this case might mean signals propagating farther than they ought.
Noise was meant in an abstract way, not statistically random noise you see in physical circuits.
Only in the superficial way in which we see figures in clouds, tree barks, etc. that we can name. Not in the sense that somebody sees a specific figure in a Rorschach test. But in dreams we have the impression of very specific semblances and "movie-like" experiences.
> in the superficial way in which we see figures in clouds, tree barks, etc. that we can name.
Exactly!
I've seen very specific semblances in coffee spills, knot-holes, etc. The reason they're not movie-like is because they're still and static, and not connected directly to my brain.
Dreams have the advantage of being on the bare wires, whereas Rorschach tests and the like are air-gapped.
For me at least, it seems to depend on why I'm sleep deprived and what I'm doing. I spent 100 hours straight through working on my dissertation (only breaks to go fetch food etc.), and felt fine for the entire period - no fatigue, no noticeable cognitive effects, I was alert and coherent - right up until I stopped writing. Then it all just hit me all at once - speaking coherently was a challenge, there was an afterimage if I looked around too quickly, my mind was full of scattered and fragmented half-thoughts (not dreaming, but a similar feeling), and I ended asking a friend to go with me to a building I'd been to hundreds (possibly thousands) of times because I wasn't sure I'd find my way there. To put it simply, I was mentally a mess, and just needed to crash for 18 hours to recover.
On the other hand, I'm currently sleep deprived due to insomnia (it's 1320 on Tuesday, and I've had less than an hour sleep since 0900 on Friday), and the effects have been much more gradual. It's a steady build-up of fatigue and general "brain slowness" for lack of a better word (e.g. I was playing Picross last night, and puzzles that normally would take me less than ten minutes took me more than half an hour), but I'm more or less fine - no visual effects, my thoughts are coherent, and it doesn't feel much different to how I'd be after a long day working (just significantly more severe).
That's amazing to me. I haven't been over 20 hours without sleep for several years, before that I think the max I did was about 35-40 hours which was enough to almost make me hallucinate. I guess I could go for longer, but at that point the only thing I want to do is sleep, any other life goals suddenly become distant second in importance.
It's certainly not something I'd recommend doing (I've had a couple of occasions where I've been up 40ish hours and started to notice the visual disturbances, so it can definitely come on sooner).
The dissertation was partly very poor planning on my part, but I also stumbled on a doctoral thesis that more or less disproved the central tech. behind my dissertation less than a week before the final deadline, which gave me two options:
A) finish up what I'd done, knowing it was fundamentally flawed and that I'd never be able to defend it if called for a viva voce (unlikely, but a definite possibility)
B) rewrite pretty much the entire thing (~30k words) to take a different approach, re-implement the hardware (audio filtering; didn't help that the spec. sheet lied to me and said it had an FPU but actually just emulating floating-point in software which was unusable slow), and come up with a convincing conclusion explaining why a year-long project produced nothing particularly useful.
I went with B, hence the 100 hours of solid work, and it went OK (mark was a marginal pass, but a pass nonetheless), but I'd hate to do it again. It took me 3 or 4 days to start feeling normal and alert again, despite sleeping 18 hours after crashing once it was finished.
The current insomnia is really weird though. I saw my GP this morning, took a fairly hefty dose of sleeping aids (15mg diazepam on top of the 20mg tamazepam and 75mg promethazine I was already prescribed[1]), yet somehow feel more awake than before taking those, despite the fact I'm only about three hours away from having had less than than an hour sleep total in the last six days. Honestly, I just feel bored more than anything at this point (hence this somewhat unnecessarily long post :p) - I don't have the physical energy to do a great deal, but mentally I feel more or less normal (though I suspect when I finally do get some sleep, it'll catch up with me and I'll have a rouge couple of days).
[1] FWIW, I've also got Zopiclone, but I saving that as a dug of last resort. The benzodiazepines cause me no side effects, but last time I used the Zopiclone it was rather unpleasant - it caused mild hallucinations (my room looked like it was bathed in a lemon-yellow light, despite it being the dead of night and no lights were on), and it had a strong amnesiac effect (my memory of the night pretty much goes "I'm in bed, why is everything yellow?", "I'm in the bathroom, how did I get here?", "I'm back in bed, but it's three hours later", and I have literally no idea what happened between each thought. It's just like a jump cut in a movie - there isn't even a hazy memory of I did something; it literally just goes from being in one room to being in other, despite there obviously being a chuck of time missing. It's pretty disconcerting).
It seems to happen while sitting down doing repetitive editing after ~40 hours wakefulness after a short night of sleep.
I'm also looking into evidence that a blood sugar deficit may have been involved. Reportedly some of the techniques used to maintain alertness can result in increased glucose metabolism coupled with the unfortunate side effect of having zero appetite.
Having spent enough time in extremely sleep-deprived states for projects recently, I've experienced firsthand a lot of funky stuff going on (e.g. falling asleep and waking up with a full page of class notes in front of me, or realizing that I've started 'dreaming' while editing a document, the dream being seeded by the words I was processing.)