To sleep, perchance to dream....?

Discussion in 'Behavior and Intelligence' started by nanoteuthis, Oct 28, 2008.

  1. nanoteuthis

    nanoteuthis Larger Pacific Striped Octopus Supporter

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    While watching CORAL SEA DREAMING, one of my fav DVDs, I noticed some sort of pretty reef fish described by the caption as "sleeping in a mucus bubble". Which I assume answers the question of whether fish sleep.

    But then I got to thinking about this whole mechanism of sleep and dreams. We all know that mammals, birds, reptiles, amphibians, and even fish sleep. But when we get to the invertebrate level, is sleep still part of the picture?

    I somehow doubt this would apply to, say, bivalves, jellyfish, corals, sponges, earthworms, protozoa, and bacteria.... but what about "higher" inverts such as insects, arachnids, crustaceans, and (you knew this was coming :mrgreen:) cephs? Do they sleep, or have a biological process similar to sleep?

    And if any of the above inverts do sleep.... do they dream? For that matter, do birds, reptiles, amphibians, and fish dream? Everyone here has seen a dog or cat wildly chasing imaginary prey in dreamland, but I don't know how one would measure REM sleep in non-mammalian species.

    Maybe this could best be summarized by two basic questions:

    1. At what point on the evolutionary ladder does the ability/necessity to sleep begin?

    And, having determined that....

    2. Among those species which do sleep, at what point on the evolutionary ladder does the ability/necessity of dreaming (as indicated by REM sleep, for want of a better criterion) begin?

    This may sound silly, but I am genuinely curious about the whole thing..... which keeps me awake at night. Literally. Steve-O'? Kat? Monty? Nancy? Anybody?

    :bugout:

    Tani
     
  2. OB

    OB Colossal Squid Staff Member Moderator

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    I think this is as always an excellent question, my dearest and most benthic buddy.

    To my understanding, the query is twofold:

    1: To which extent does the complexity of the neural network as such give rise to "random firing" (for reasons of "chaos" organising itself through nominal feedback) in the rest state.

    2: Does the ability of "memory" equate the possibility to dream?

    Addendum: at which level of consciousness/self awareness do neural activities become "experiences" or "dreams"? I would say a lot earlier on in evolution than most would feel comfortable with from a classic man/nature division point of view.
     
  3. monty

    monty Colossal Squid Staff Member Supporter

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    I think this is a tough question, largely because we know so little about the evolutionary origins and purposes of sleep.

    My completely wild guess is that sleep as we know it is an evolutionary quirk more than a necessity for a system to be a proper brain, so I would not be at all shocked if it happened to develop in an early vertebrate ancestor and became locked in, which would lead me to think it might not be present in invertebrates. However, maybe it, or a precursor that makes it inevitable, developed with the first nervous systems, and made any sufficiently complex brain require it in some form.

    I can't see any reason why sleep would be mandatory, so my :twocents: is that it all depends on whether the precursor for sleep was present in our last common ancestor with cephs (a rather long time ago, likely Precambrian.)
     
  4. robyn

    robyn Vampyroteuthis Supporter

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    This is such a cool topic... I disagree with Monty slightly in that I don't think sleep or its analogue need be present in the common ancestor of cephs and mammals, but instead that 'sleep' is something that arises in concert with some minimum biological level of neural complexity. I'm not certain that it need be concurrent with an ability to form memories, but I agree that one purpose of dreaming is in reconsolidation and possibly extinction of memories.

    As for cephs specifically, there is at least behavioural evidence of sleeping in octopuses (pupil contractions, reduced colour changes and lowered respiratory rates), and evidence that 'sleep deprivation' on one occasion results in rebound sleeping in the next sleep cycle. Which is very cool, but I agree that its a complete mystery still to ascribe a 'purpose' to sleeping in species as remote as molluscs and mammals.

    So, in conclusion, I really have no idea. But its a great discussion topic. I hope more people will weigh in here.
     
  5. Architeuthoceras

    Architeuthoceras Architeuthis Staff Member Moderator

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    Is "instinct" a form of dreaming? Did ammonoids dream of going to the spawning grounds? Do squid dream of going to the spawning grounds? Do turtles dream of going to a specific island at a certain time in their life? Surely they dont just end up where they need to be by chance, something tells them where to go. Could it possibly be dreams? I know I often dream of going to the spawning grounds, and I dont need to be sleeping. :wink:
     
  6. monty

    monty Colossal Squid Staff Member Supporter

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    Hmm. I guess the real question is "is sleep something that's important to higher mental capabilities?"-- it sounds like you think it may be, while I'm not so sure. Computers don't need to sleep, but they don't exactly think, either.

    One analogy is that a memory-related structure found in many (all?) vertebrates is the hippocampus, but in cephs, there is a rather different-looking vertical lobe system. Perhaps as we explore, we'll find that there are parallels between the two, perhaps even including a need for sleep, but it's also possible cephs have evolved a completely different system to address the same problems of memory and learning.

    In the case of eyes, vertebrate and ceph eyes are quite similar, but arise from different germ layers (IIRC) and are "inside out" relative to one another. I think that's a sign that there are aspects of eyes (lenses, retinas, pupils) that are fundamental to any animal developing vision. Is the same true of sleep? I have no idea.

    All I really meant was that there seem to be 3 possibilities,

    1) cephs don't sleep (which appears to be ruled out somewhat)

    2) cephs and humans sleeping is convergent evolution, and arose because of similar evolutionary needs once their intelligence rose to some level (this is how I read Robyn's post...)

    3) some common ancestor had a primitive sleep precursor, and that favored the evolution of sleep in both groups (this is my earlier thinking.)

    Do any other intelligent-ish animals sleep or not? Spiders sit idle for long periods, I'm not sure about stomatopods, and bees seem to be idle in hives sometimes... I don't know if any of those should count as "sleep," though.

    We really need to find extraterrestrial life and see if it sleeps...
     
  7. DWhatley

    DWhatley Cthulhu Staff Member Moderator

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    humm, a week in the mountains with an attractive student and you start relating to your more recent cavemen ancestors :roll:. Your statement does bring up a question as well. Is it necessary to sleep to dream or is being asleep part of the definition of a dream?

    Is anyone aware of studies done regarding sleep and internal repair? I have always been under the impression that sleep allowed the body to be active internally to do all the housework where awake time used similar energies to mobilize the container. If there is any merit to that folk understanding then it would make sense that any organisim (as a group, not individually) that is daily battered from its environment (thinking octo arms specifically) and needed to regenerate parts (all those new cells!) would require sleep and the need would be encoded so that even if the environment was friendly, the need would still exist.
     
  8. Animal Mother

    Animal Mother Architeuthis Supporter

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    Wow. I think I'll stick to the kiddy pool. It's way too deep in here.
     
  9. monty

    monty Colossal Squid Staff Member Supporter

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    Aw, the funnest discussions are when there are unanswered questions that might be answerable with the right cleverness and perhaps some investigation.... stick around, 'cause "Adult Swim" is just late night on the cartoon network...
     
  10. OB

    OB Colossal Squid Staff Member Moderator

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    Einstein was working at a patent office when he rewrote physics, so indeed, stick around from outside of the box! I am inclined to stick with my initial argument that dreaming arises from a minimum level of complexity and the presence of memory. With the reasons for sleep, I am a lot less certain. It could simply be that energy conservation has an evolutionary benefit as a trait? The disturbing fact is, that sleep deprivation kills, so the conserved trait must be about a lot more than mere savings; it has become essential.
     
  11. nanoteuthis

    nanoteuthis Larger Pacific Striped Octopus Supporter

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    Wowie, looks like I started something here.... cool! :sun:

    Being essentially on a kindergarten level re biology -- at least compared to most of y'all -- I'm grateful for all these fascinating responses.

    Regarding the necessity of sleep: As Ob pointed out, sleep deprivation can indeed be lethal, so I agree that it must be more than just an ancient evolutionary quirk which persisted in more complex species. And I don't buy into the oft-repeated (on nature shows) theory that sleep is a mechanism to protect an individual from nocturnal predators.... aside from the fact that there are a whole lot of diurnal predators, being asleep would -- if anything -- make the individual more vulnerable to predators.

    On the other hand, D's theory that sleep "allowed the body to be active internally to do all the housework where awake time used similar energies to mobilize the container" makes perfect sense to me, as does Ob's Ob-servation that "energy conservation has an evolutionary benefit as a trait".

    As for dreaming -- as far as I know, at least in humans, it is also a necessity. One of the side effects of prolonged sleep deprivation is visual hallucinations, almost as if the "dreaming" mechanism suddenly breaks into the waking state after being suppressed for too long.

    Which begs another question: Which came first, dreaming or sleeping? I really like Architeuthoceras' comment about dreaming being the equivalent of instinct.... subconsciously driving cephs and sea turtles (and TONMOers :smile:) to the appropriate spawning grounds at the appropriate time. An additional function of sleep could be to facilitate dreaming -- a vital way of processing information and memory -- since too much "daydreaming" would certainly interfere with an organism's other survival functions.

    I was also unaware that cephs go through cycles which resemble sleep -- thanks to Robyn for that information. And thanks to Monty for the insight into possible parallels between ceph and human morphology. Monty, I like the idea of a combination of the second and third possibilities you listed.... i.e., that a primitive precursor to sleep existed in a common ancestor of cephs and humans, that it developed somewhat differently in both evolutionary lines, but that over the eons convergent evolution led to a function which appears similar in humans and cephs. (Does that make any sense? As a non-scientist, I'm having trouble expressing myself accurately.... :bonk:)

    I think I have turned my own limited brain inside-out in an effort to understand all this complex information, but I'm enjoying the process immensely!

    Cheers,
    Tani
    (who can vouch for the negative effects of sleep deprivation in online Scrabble players)
     
  12. nuro

    nuro Pygmy Octopus Registered

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    theories on sleep

    a recent article i red(dont remember where) theorized sleep was actually a form a life practice, training us for situations that could arise. studies of an idian culture in south america showed that many dreams focused around a particually toxic insect in the area and rarely where as abstract as those we have. one theory on why we have such odd dreams at times is thought to be due to our broad range of daily experiences including movies and other highly imaginitive activities.

    i was fascinated by this idea becuase, to me, it made alot of sense.. sleep maybe required in advanced organisms for physical reasons but mental as well..why cant that tiem be used as "practice" time for somethign dangerous we may have to react to in the future if the brain is capable of simulating that.


    on the ceph side of things ive withnessed my octo twitching when sleeping.
     
  13. Shanks

    Shanks Cuttlefish Registered

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    I've been meaning to start keeping a "dream journal" near my bed at all times so that I can write down what I remember of my dreams as soon as I wake up, because I have some pretty whacked-out dreams. I've always thought of dreaming (from a layman's point of view) as an odd quirk of having a higher functioning brain, but sleep itself being a necessity with the purpose of repairing the works.

    I've read in places that one of the functions of sleep is the reprocessing and storage of memories, so let me take a wild stab in the dark and suggest that maybe all animals that sleep have to dream, because maybe as a consequence of the brain going through all of these memories, it hashes some of them together and it "replays" through the mind? I'm thinking of this mechanism almost like when a computer hibernates: it has to dump the contents of the RAM onto a sector of the hard drive... maybe that's what our brains do when we dream, and during the transfer we re-experience these things.

    Who knows. Well, probably a psychologist, and I'm certainly not one of those. I'm experiencing my own endeavor into sleep deprivation as I type this at almost 4am Chicago time. Very interesting things to twist our brains around...
     

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