Wikipedia:Reference desk/Archives/Science/2015 July 6

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July 6

Sleep immobility

Is sleep paralysis the same state when you fall asleep in a potentially unpleasant position (for example, with head pressing against your arm) and later start to feel numbness due to disrupted blood flow, but is unable to move or wake up? I'm healthy, but had at least one such experience in the past, and this is really a nasty thing. Brandmeister^talk 08:51, 6 July 2015 (UTC)

No, these are quite distinct phenomena. Sleep paralysis involves a more or less complete (though typically very brief) loss of volitional motor function for the whole body, usually occurring during either hypnagogia or hypnopompia (the transitions between full wakefullness to sleep and between sleep and wakefulness, respectively). It results from irregular function in the neural pathways which regulate these states of consciousness and restrict volitional movement when we sleep, lest we act upon mental stimuli while we sleep; sleepwalking, accordingly, is in some sense the inverse of this condition in which those circuits do not operate appropriately while asleep, allowing movement. Sleep paralysis is therefore more or less completely the product of the central nervous system. By comparison, a limb "falling asleep" from pressure on a nerve or the surrounding tissue (with the experience being clinically known as obdormition with regard to the numbness, and parathesia with regard to the telltale "pins and needles" sensation) does not usually involve significant impairment of motor function or proprioception and is best defined as a matter of physiological disruption of the relevant area of the peripheral nervous system (though similar numbness in limbs can, in rare instances, result from brain tumors or other CNS dysfunction). We all, of course, have experienced the sleeping limb phenomena every so often. Most people also have a memory of experiencing sleep paralysis once or twice in their life -- these events (or at least the fully conscious variations which one can later recall) are usually highly transient and exceedingly rare, but there is also a chronic version of the condition in which episodes can last longer and occur more frequently. I do agree, it can be an unsettling experience, even when not fully awake. Snow ^{let's rap} 10:20, 6 July 2015 (UTC)

@Snow Rise: I've always read that sleep paralysis affects motor function without mention of the sensory, and certainly people are sensitive to touch when asleep... yet I've had the personal experience during gout attacks of intentionally maintaining sleep paralysis in the lower part of my body for close to an hour (I think) after reaching wakefulness, during which there was no pain. It was only after "breaking" the sleep paralysis that the pain started. I'm still not sure of the explanation for this. Wnt (talk) 13:57, 6 July 2015 (UTC)

I think you're referring to something unrelated, but I can confirm that I've experienced it as well. For example, if I'm suffering from a cold, I may wake up feeling quite well only to suddenly feel worse after I begin moving. Or, as in your example, a painful or itchy appendage seems to quiet down during the night only to come roaring back as soon as I start moving. I'm curious about the mechanism; I've just assumed that it was due to laying still. Matt Deres (talk) 19:39, 6 July 2015 (UTC)

That's interesting indeed. I've not heard of an instance of a person willing themselves to be unable to move before - and indeed, the idea of volitionally maintaining an inability to engage in any physical act seems somewhat counter-intuitive to me. Do you mean that you simply did not move your lower muscles at all and put yourself in a headspace where you were focusing on what the sensation of not being able to is like? What degree of wakefullness do you recall experiencing? I will say that, as a general rule, nocireception is a highly modal phenomena, often significantly influenced by state of mind, level of consciousness, and other psychological and neurological factors. And then too, it's just as Matt says -- there is a local physiological factor in that gout is a form of inflammation, which can be exacerbated by movement (though as you would well know, a lack of movement does not in itself guarantee an absence of pain). Since I assume the "breaking of the sleep paralysis" yous peak of coincided with volitional movement, I would think this can't be discounted as a factor in this instance, though certainly that doesn't altogether discount some peculiar and uncommon biopsychological effect if you felt genuinely paralyzed, but with the episode lasting as long as it did, I would suspect it was not your typical sleep paralysis but, at least at some point, closer to a kind of self-hypnosis. Snow ^{let's rap} 00:03, 7 July 2015 (UTC)

@Snow Rise: Well, it seems like when I'd had a more 'authentic' sleep paralysis feeling in my childhood, that there was a sense of being unable to move, but that with enough effort, a very slight motion could be made that then would dispel the paralysis. The closer to 'awake' I was, the less effort would be required. The extreme end of that is waking up but still feeling like my limbs aren't actually online somehow until a miniscule effort is made to move something. It seemed like my head could, briefly, be moved without dispelling the paralysis in my legs, and perhaps even arms for a few seconds, but I think moving one part tended to make the 'paralysis' end in the others pretty quickly. (My experimental technique is questionable here since I was doing it only during attacks that should have been avoided, while half asleep!) There's an instinct to just stretch and bring everything online immediately, but a gout attack definitely makes a person hesitate to move anything without thinking... which makes it more feasible not to do so. I should add that during wakefulness, not moving my feet for hours on end would do much less to reduce the pain - the difference is between a very slight lessening and its total absence!

I should add that the nature of the 'paralysis' is not simply a limpness of the muscle. I am personally inclined to attribute things like a stiff neck to falling asleep with a muscle still contracting, and then it stays that way until one becomes aware of discomfort. (Which is a much weaker sensation than what is felt after waking!) Since I avoid doing that I haven't had such trouble in a very long time. I recall such oddities as falling asleep with a college textbook held up above me, and waking up when it fell on me something like an hour later because I'd been holding it the full time, with the stiff sensation in my fingers and hand to prove it. I feel like the sleep paralysis instinct is a perhaps vestigial, or perhaps simply untrained version of an instinct that is supposed to let an ape sleep safely in a tree, holding onto the branches, and so this seems to make sense. But all this is just speculation!!! Wnt (talk) 13:07, 7 July 2015 (UTC)

Interrupted blood flow would mean limb death, not just tingling. It is sometime possible to tell which nerve is compressed or trapped by part of the limb is tingling. For example, it is sometimes possible to compress the nerve on the outside of the elbow through flexion. The middle finger, ring finger and pinky will go numb. A different posture compresses the nerve for the index finger and thumb and they will "fall asleep" in that position. A lot of people don't remember which finger and just remember "hand is tingling." The specifics are good for determining carpal tunnel syndrome or what type of sleeping posture fixes it. --DHeyward (talk) 11:28, 6 July 2015 (UTC)

Re: "Interrupted blood flow would mean limb death" ... that would depend on how long and how complete the interruption is. StuRat (talk) 21:04, 6 July 2015 (UTC)

The OP actually said "disrupted", unless it's effectively the same thing. ←Baseball Bugs ^{What's up, Doc?} carrots→ 21:23, 6 July 2015 (UTC)

Is it also due to peripheral nervous system's disruption mentioned by Snow that I can't typically awake (or force myself to awake) and correct my numbness-inducing position? I.e., in such state I couldn't do anything about it, being forced to wait until some critical point when it resolves by itself. Brandmeister^talk 22:25, 6 July 2015 (UTC)

The word you need there is "awaken", meaning "to become awake", although "wake up" is more common in casual conversation. Since you repeat the word, I would use both: "...awaken (or force myself to wake up)...". StuRat (talk) 14:55, 7 July 2015 (UTC)

Looking for research study paper on Fibromyalgia

Hello, I had come across an article on Fibromyalgia and wanted to read the study paper that was related. Unfortunately http://guardianlv.com/2013/06/fibromyalgia-mystery-finally-solved/ did not point to where to get the paper on painmed.org and I am having difficulty trying to find it on this site, as it doesn't seem to host a database (pay or otherwise. Dr. Rice is the name of the senior researcher. Is there a place I can find this paper? Thank you. 67.234.207.4 (talk) 19:56, 6 July 2015 (UTC)

The original research article is here [1]. I googled /Frank Rice Fibromyalgia/, first hit was here [2], which appears to be a nicer, slightly more detailed general-audience summary. INTiDYN seems to be a spin-off business the authors are associated with. Since the latter article includes a Digital_object_identifier reference at the end, I just had to pop that in to http://doi.org to get it to resolve to the original research paper, which seems to be freely accessible. If you have questions about the content of the article feel free to come back for clarification. SemanticMantis (talk) 21:31, 6 July 2015 (UTC)

Oh, here's an even better lay person summary by Dr. Rice [3]. To answer a question you didn't ask - painmed.org is the web page for the professional association. All journal publication and distribution is handled through Wiley [4]. (Fortunately someone paid Wiley US$3,000 [5] on behalf of the authors to make that link accessible to you. Even though Wiley did not pay for the research, or the reviewers, or any of the other costs of research, they seem to think it's reasonable to charge that much to put a pdf on a web page... and they are big enough that they can get away with it. /rant) SemanticMantis (talk) 21:42, 6 July 2015 (UTC)

Elephant seals and rape

Is it true that in every instance of elephant seal copulation, it is the case that the male elephant seal rapes the female elephant seal, and the female elephant seal is never receptive to sex? Malamockq (talk) 21:55, 6 July 2015 (UTC)

I'm not seeing any indication of that in Northern elephant seal or Southern elephant seal. ←Baseball Bugs ^{What's up, Doc?} carrots→ 22:05, 6 July 2015 (UTC)

Our rape article is crowned with the hatnote "For rape among non-human animals, see Sexual coercion." Elephant seals are mentioned a couple of times in that article. -- ToE 22:20, 6 July 2015 (UTC)

Even so, if that's how they reproduce, then that's how it is. Animals are not subject to human morality laws. ←Baseball Bugs ^{What's up, Doc?} carrots→ 22:28, 6 July 2015 (UTC)

From this description of Northern Elephant Seal reproduction:

Males do not court or investigate the perineal area of the female prior to mounting; they seem to be testing the receptivity of the female. They mount from one side without any preliminaries and seemingly attempt to overpower the female. Males use the great bulk and weight of their forequarters, a fore-flipper clasp, and a neck bite to restrain the animal. They mount pregnant females, those giving birth, females soon after birth, and females in estrus. Only the frequency not the form of these mating attempts varies with estrus. A mount may end in copulation; by the mounter being repulsed by an alpha; or simply because the male ceases the attempt.

Females respond to male mounts by active protest or passive acceptance. A female protests by issuing a virtually continuous train of vocal threats and by whipping her hindquarters vigorously from side to side. Because of their relative positions her rear flippers often strike near the males penile opening. She may also flip sand directly at the males head and face, nip his neck, or struggle to get away. Alternatively the female may remain passive throughout the mount or may facilitate by spreading her hind flippers. Females were not observed to court or solicit copulation.

Estrus as well as non-estrus females protest the majority of mounts attempted by males. ... [This is followed by analysis from a study of 1500 mounts, only 7% of which were not protested.]

Early estrus females protest all mounts. As estrus proceeds protesting is reduced. No-protest is the most common response on the last day of estrus. ... [This is followed by further description of mounting behavior.]

Females near the end of estrus rarely protest mounts and readily accept copulation with peripheral males. During the last hour on land females were extremely receptive to all males.

So the answer is, no, it is not true that the female elephant seal is never receptive to sex. -- ToE 23:03, 6 July 2015 (UTC)

Rape is a human behaviour. If female elephant seals wanted to avoid copulation they would have evolved a mechanism to do this and of course, the species would have become extinct. This clearly has not happened. There are many reasons why a female might appear to be unreceptive to a male - one of these is that she is assessing the fitness of the male.DrChrissy ^(talk) 23:06, 6 July 2015 (UTC)

There is some information at Anthropomorphism#In science may be relevant to this discussion for some readers. MarnetteD|Talk 23:26, 6 July 2015 (UTC)

@DrChrissy: Evolution certainly has no concern for what the females 'want'. Wnt (talk) 00:13, 7 July 2015 (UTC)

I'm afraid evolution has everything to do with what the females 'want'. We are talking here about the motivation of animals. Evolution serves to produce the fittest animals. As pointed out below, females are motivated to mate, but they are also motivated the produce the fittest offspring. Therefore, they have evolved behaviours to ensure this. The females are motivated to mate, but choose who they mate with. I think this thread would have been better if a definition of "rape" was given/discussed - not a criticism, just a comment.DrChrissy ^(talk) 11:23, 7 July 2015 (UTC)

@DrChrissy: I think @Wnt: is speaking from the perspective of Ethology - we cannot ever know an animal's desires, we can only know their behavior. I think you might have been speaking from a more teleological perspective, by which we can often use shortcuts like "want" to describe the end results of a set of behaviors or evolutionary processes. There's lots of things that come in to this elephant seal situation that haven't been linked - sexual conflict, sexual selection, and mate choice cover most of the theoretical context by which scientists would address these behaviors. I totally agree that using the word "rape" confuses the issue, though it also provides an opportunity to clarify the issues. An example that the OP might be interested in - bedbugs reproduce exclusively via traumatic insemination. In short, females have no vaginal opening, and males simple spear into female abdomens with a harpoon-like penis, flooding the abdominal cavity with sperm, some of which manages to fertilize eggs. This can even lead to weird situations where homosexual contact can lead to pregnancy - if a male A spears a male B while B is currently spearing a female C, some of A's sperm can impregnate C! Fascinating stuff, and surely the result of evolutionary processes, but not anything to do with want or rape. SemanticMantis (talk) 14:41, 7 July 2015 (UTC)

Good reply, but actually, it's not what I meant. It's more that it doesn't matter what seals (or people) actually want, but only what they do. For example, think of how many companies run their workers ragged with swing shifts and surprise overtime, when they could just as easily plot out a regular schedule. By keeping their workers miserable, off-balance and insecure, they make it harder for them to look for better work or stand up for their rights. It doesn't matter what the workers think - as long as what they do is desirable to their rulers, that's what counts. Wnt (talk) 16:44, 7 July 2015 (UTC)

But that's also the ethological approach - actions/behaviors are what matter the most (and also have the benefit of being objectively observable). But IMO it's also a bit naive to think that selection can't act on motivations/desires/taxis/whatever you want to call it when a bug or mouse (or plant ;) does one thing instead of another. Of course it's the end result that matters the most, but the whatever notion of "want" is also amenable to adaptation and selective influence, if for no other reason than these "wants" influence behavior. Likewise with your business example, eventually wants can matter if they lead to a Strike_action. SemanticMantis (talk) 17:37, 7 July 2015 (UTC)

Actually, I think we need to invoke the Selfish gene principle. We are all just secretions of our genes. Some of our genes have coded for eye colour, our behaviours and yes, some genes have somehow coded for our motivations. What a great and biologically inexpensive way for genes to perpetuate themselves!DrChrissy ^(talk) 17:45, 7 July 2015 (UTC)

It is in the females(cows) interest to mate. That is why they go onto the beach with a bull, I seem to recall they may even choose which bull to mate with, by going to his territory. Whilst the mating season is on, bulls do not leave their beach and territory, surviving on stored energy, water and protein. The cows also have an issue, they want the best quality sperm so that they can conceive, and want it when they need it.

Supposing a bull has two cows on his beach. He mounts the first, who protests because she is not ready. He then mounts the second who is on heat, she gets all of his sperm. A week later the second cow might protest, he moves his attention back to the first, who is now on heat and accepts him. The first cow now gets more sperm, and a higher chance of getting pregnant.

In short, both cows and the bull win by consensual matting. If the bull rapes all cows he will be wasting sperm, and the cows will have less chance of conceiving. Martin451 01:08, 7 July 2015 (UTC)