Would hypnagogic images or early sleep onset images be outside your particular province of research? Any idea if they (and perhaps dreams, too) are just products of low-level “noise” in an inactive visual system? What’s the latest thought on them?
I ask because such images fascinate me. I used to experience them a lot then when my life was busier (but not so much anymore as I near perfection in the art of idleness).
It occurs to me that if sleep and dreaming are part of “memory consolidation and learning,” as Robert Stickgold says his research has demonstrated ( for instance ), then hypnagogic images and dreams would be more likely to appear (or be noticed) during the times in a person’s life when he is intensely involved in a new activity which might be a new job, a new sport, even a new marriage …
This seems to true in my own case. Stickgold’s Tetris study (linked to above) reminds me in particular of a few years ago when I was obsessed with playing pool; often while going to sleep on days when I had played for a few hours I would get vivid images of particularly crucial table layouts I had faced that day. I would see configurations of balls I had studied intently in order to find the most efficient paths to sinking them all. Some of those configurations I can still recall today. I suspect the athletes, baseball players and golfers specifically, we hear talking about long-ago pitch sequences and how they’ve played certain holes in years past must also experience such images in the early stages of sleep.
Della I read a book, fiction, many years ago (title forgotten) anyway it seems that in the book we sleep because in a far distant galaxy there is another “us”.
I’ve always felt intuitively that a major function of sleep is to take short-term memories accumulated during the day (or whatever) and organise them, putting some into long-term storage, and discarding others. For me, when I’m getting sleep-deprived, one of the most noticeable changes is that I stop functioning consciously - that is, I’ll do something on autopilot, but not realise I’ve done it. It kind of feels like my brain is having trouble recording new stuff, so I figured that it means the local memory is full. Plus, often it seems to me that you’ll forget something after a night’s sleep, while other times you’ll have a stronger memory of it. This could even go some way towards explaining what dreams are - if your brain is comparing the day’s memories with various long-term memories, the consciousness-farts that result could resemble dreams.
Incidentally, has anyone ever noticed that if you’re practicing some skill before going to bed, and then try it again first thing in the morning, you’ll sometimes be much improved even though you didn’t practice at all in the interim? That happens to me sometimes, although admittedly it might just feel as though I’ve improved because last time I tried the skill I was tired.
Anyway, anecdotal evidence, I don’t actually know what I’m talking about, etc. </wildarse hypothesis>
You ask a question about sleep; a trained sleep researcher turns up - and this rubbish is what you ask her?!
I saw a film which explained we are all asleep all the time, everything you think is a created fantasy and that machines feed on our energy. Far more plausible than your scenario. :rolleyes:
Wow, there’s a lot more interest here than I thought! Cool
I’m going to be pretty busy today, so I may not get back to everyone immediately. (I’m defending my dissertation in 23 days, so I have a few things to do).
Well, not only have other people noticed that, there’s gobs of research backing it up. One of my favorite studies on the topic trained subjects on a simple motor task then tested them 8 hours later. Half the subjects slept during the intervening time, and half the subjects just went along with their day as normal. When they tested the subjects after 8 hours, the ones who had slept were significantly better at the task than those who had not.
Ooh, this gives me a chance to get up on one of my favorite soapboxes. Don’t pull all-nighters, people! Just don’t do it! You’re not helping yourself learn anything new. You won’t remember it for the test, and even if you do, by some miracle, remember enough to squeak by, you won’t remember the info in the long run. Plus, the rest of your day (and sometimes more) will be shot! Just do yourself a favor and get some sleep, if only a few hours.
This subject is a bit out of my expertise. I study infant rats, and we can’t really study their dreams. The study of dreaming in humans is a messy affair, at best, consisting of waking a person up when they’re in REM sleep and asking then what they’re dreaming about. While I’ve tried this in my rats, for some reason they’ve never answered me.
Anyway, with that disclaimer out of the way I’ll throw some of my pet theories out there. Although there’s not a crazy amount of research backing me up here, I think you’re on the right track with your thoughts. Furthermore, I’ve had similar experiences.
One of the major principles of neuroscience is the Hebbian hypothesis, or, simply stated, “neurons that fire together wire together.” That is, two neurons repeatedly activate each other, the connection between them will be strengthened. It’s thought that dreams act as a kind of “mental replay,” activating the same neural circuitry that was used during the day for a specific activity. Under the Hebbian hypothesis, this would strengthen these connections and effectively implant them into memory. (It’s time for another disclaimer, though. Although we know a lot of the mechanisms and neural structured involved in the formation and storage of memory, we don’t have everything nailed down yet. We still don’t know where or how memories are stored, but there are lots of good scientists working on that.)
My personal theory about dreams is kind of esoteric. If you have a pet dog or cat you’ve likely seen them moving their paws, tails, and faces around while they’re asleep. They’re twitching. It’s commonly thought that the critters are acting out their dreams (Oh, look, Rover is chasing rabbits!), but, since that’s an utterly untestable hypothesis, I opt for a different interpretation.
Recent research has demonstrated that twitches of the limbs are involved in the formation and maintenance of maps of the body (called somatotopic maps) within the brain. Twitching is very prevalent during the time when the brain is rapidly developing and these maps are forming, and twitching has been seen in pretty much every muscle group, from the limbs to the intraaural and extraocular (inside the ear and eyes) muscles.
I personally think that dreams are “twitches of the brain.” Recently-activated neurons are firing, replaying their activity during the day, and strengthening those connections in a Hebbian fashion. Perhaps random firing within the visual system generates some visual dream images, while firing within the auditory system generates sounds. As I said before, rampant speculation, but I like the theory.
I’ve always kind of imagined it this way. As if all the sensory data you took in that day needed to be sorted out and transitioned into long term storage by doing a shut down.
If the shutdown isn’t done properly (similar to just pulling the plug on a computer that has several programs running) you lose the data you worked on that day.
That’s why I’ve assumed when someone gets into a traumatic accident that knocks them out cold they often don’t remember what happed that day previous to the accident. Improper shutdown.
Mammals and birds, as far as I know. Reptiles and other ectotherms ("cold-blooded animals) are different because ambient temperature has a large influence on body and brain activity. I don’t have much direct experience with this (although I have done some research on thermoregulation and how it effects sleep expression), but from what I’ve gathered, in ectotherms some properties of neuronal transmission change with the ambient temperature, speeding up at higher temps and slowing down at lower temps.
Fish are another story altogether. Some fish (including sharks) have “heaters” that are found around their brains and eyes, allowing them to function normally even when the ambient temperature is very low.
Thermoregulation and sleep go hand in hand. If the ambient temperature is too high or too low you’re less likely to sleep. This is partially due to the fact that when we sleep we lose control of temperature regulation. I don’t fully understand all the mechanisms behind it, but it’s a pretty interesting interaction.
Thanks, Della. The idea of brain twitches pleases me beyond all reason (and also makes me want to find out all I can about Charles Bonnet Syndrome, which pathology I’ll walk out on a limb to suggest just might also have some little thing to teach us about dreams, sleep, and our ravelled sleeves of care). And thanks for pointing me to Hebbian theory.
Oh, and if your infant rats do start telling you their dreams, please don’t keep it to yourself.
- and this rubbish is what you ask her?! 
