Sleeping is such an essentially absurd activity. We run around frantically during the day, then suddenly we need to lie down and keep quiet for a few hours, only to get up and run around once more. It's a curious cycle that needs to be repeated at regular intervals throughout a healthy life. There is a misconception that sleep is a restful state - the opposite of being awake - simply because we don't move much during sleep. The truth is that being asleep is not akin to being unconscious at all; it is very much an altered state of consciousness. In fact, we spend our lives in three states of consciousness: wakefulness, NREM sleep and REM sleep. Although two of these states are lumped together as 'sleep', they are very different from one another. NREM (non-rapid eye movement) sleep is divided into four progressively deeper stages, culminating in slow-wave sleep which is characterized by rolling delta brain waves on an EEG. Ho-hum. So far sleep doesn't seem that exciting. But as soon as the brain enters REM sleep, dynamic changes can be observed. To the researcher monitoring a sleeping person's EEG, the brain waves would suggest that the sleeper has woken up after the 90 or so minutes spent in NREM sleep. Heartrate and breathing are irregular. The body is responding to some sort of stimuli. Yet the sleeping individual is definitely not awake and lies still, the only movement being that of the eyes under closed lids. The stimuli are not entering from the outside environment through the senses, but are internally generated. It is the only instance when the brain hallucinates and we consider it normal and healthy. This psychosis is more commonly referred to as dreaming. REM sleep is a fascinating but difficult aspect of life to study. What is it for? Why is the brain so active during REM sleep? Why do we dream? One thing is clear: sleep is essential for survival. Sleep heals wounds and stimulates the immune system. We know that reduced sleep significantly increases one's risk of getting involved in accidents, simply due to fatigue and impaired responsiveness. Total, extended deprivation itself can also be fatal: in one study, lab rats died after 11 to 32 days of being denied any chance of sleep, and from 16 to 54 days if selectively deprived of REM sleep only.
The psychedelic splendour of REM sleep! That warm and inviting abyss of dreams. Turn on, tune in, drop out; no acid required. REM atonia ensures that we don't act out our dreams. This is fortunate for those sharing a matress with a fellow dreamer. The motor neurons that control muscle movements are selectively inhibited as REM sleep is initiated. Sometimes this inhibition is triggered before REM is initiated, or persists for some time after a REM phase. When this happens, you find yourself at the interface between sleep and wakefulness, unable to move. Welcome to the land of hypnagogia, where input from the senses is taken by the brain and stretched, distorted, and expanded through iterations of its own design. This is actually the state you normally pass through on the way to dreamland. However, when REM atonia is accidentally coupled with these sensations, people often feel a 'presence' in the room with them, or a fear-inducing pressure on their chest, an inability to breathe. Voluntary breathing is suppressed under REM atonia and is replaced by involuntary breathing controlled by the brainstem, see. Nothing to fear. Yet we don't want to relinquish that conscious control. The anxiety brought about by such incidents of sleep paralysis has given rise to a myriad of legends about crushing demons, maras and the incubus. And all reports of alien abduction from bedrooms, I expect. Apart from the unlucky few who experience it every night, the majority of sleepers will experience sleep paralysis at most once or twice in their lives. So don't be alarmed and enjoy the ride - after all, you engineered it yourself.
REM sleep disorders are teaching scientists all sorts of things. From how the consolidation of memories works by reinforcing them with biochemical loops in new connections between neurons (you may have to read that again), to fascinating breakthroughs in the relationship between sleeping and eating. Yes, the two are connected. If our requirements for energy, shelter and procreation were somehow met by proxy, would we spend our whole lives asleep? Perhaps that's our true baseline state of being. Apart from sophisticated genetic mechanisms that ensure we live our lives according to circadian rhythms, there are others that trigger wakefulness in response to changes in energy reserves. Small proteins called orexins (or hypocretins, depending on which research team you talk to) are produced by a couple of cells in the hypothalamus for just this purpose. These proteins are the brain's own breakfast bell. Interestingly, when this bell malfunctions, either through mutations in the genes for the orexins themselves or in the genes for their receptors, narcolepsy results. This intriguing sleep disorder really warrants a post of its own. I plan to share my thoughts on this remarkable story in a future piece. It's a tale of obese mice, sleepy dobermans, collapsing teenagers and some of the most elegant experiments in all of molecular biology.
All mammals sleep; we all require it to live. So I'll leave you with some final thoughts about whales. Cetaceans (that's whales and dolphins to you non-biology types) never enter NREM sleep with both hemispheres of their brains at the same time. This is called unihemispheric slow-wave sleep. In fact, they sleep with only one eye closed - the left when the right hemisphere is asleep, and vice versa. Good thinking, to prevent sinking. And drowning, that certainly wouldn't be conducive to the survival of the species at all. Bottlenose dolphins sometimes rest on the bottom, or seem to just float for a bit. More commonly, they slowly swim counterclockwise while sleeping, even when switching brain hemispheres. Smaller dolphins and porpoises are always on the move from birth until death; they are never immobile, the hallmark of terrestrial sleep. Sleep is anything but a restful, unconscious state. Here is the weird thing, though: nobody has ever published accounts of REM sleep in cetaceans; they are the only mammals studied in which this state has never been observed. How do they survive without the third state of consciousness? Why does REM sleep exist, then? How does learning and the consolidation of memory occur? Do dolphins dream?
Maybe I should have read this before publishing my last post. I know that New Years resolutions are ridiculous but it was time.
You've chosen a good one. I could do well to try and get some restful sleep too. I couldn't help but wonder if my sleeping habits are similar to that of the bottle nosed dolphin. How else do I end up facing the opposite direction with the sheets swirled around my legs?
Fascinating post. How does your brain fir through the doorway?
Good resolution. Maybe I should consider the same one? I long for sleep...lots and lots of sleep...
I have suffered from sleep paralysis for many years. It doesn't happen much anymore, however as a teenager, I dreaded going to bed every night. I was also suffering from PTSD with nightmares, so I was obviously sleep deprived as well. I have a son who has juvenile myoclonic epilepsy. This is an epileptic disorder that is directly affected by and related to the sleep cycle. Fascinating that the cetaceans haven't been shown to experience REM. Maybe they do but it just hasn't been verified scientifically yet. As always, EOH, very interesting post :)
hmmm.. i think i need to catch some of them ZZZ's...
Happy New Year, eoh!!!
OMG! This looks like a fantastic post. I will need some time to read it. Will be back later.
Once again, you haven't disappointed! What an interesting post!
I've never learned about Cetacean sleep cycles before-- fascinating! I'm suprised that they swim counterclockwise even when their right hemisphere is sleeping. My first thought was that they would keep the "seeing" eye looking toward the outside of their swimming circle for protection.
Perhaps REM sleep requires both hemispheres. How is sleep different in reptiles or birds? Do they have REM cycles? (You're making me want to back to the campus library-- too bad I live an hour away from my alma mater!)
I can't wait to hear about the elegant narcolepsy experiment!
Another awesome post.
I've experience sleep paralysis a couple of times and can attest to the sense of presence in the room. It's fascinating to me that this biological phenomenon probably accounts for stories of the incubus, among others.
I didn't know about cetaceans! Thank you for adding to my knowledge today.
Sjoe! Hierdie is baie, baie interessant. Ek sal graag meer hieroor wil lees. Ek het al gaan slaap, met 'n wiskundige of programmering probleem in my agterkop en dan skrik ek in die middel van die nag wakker en het die antwoord op die probleem. Hoe gebeur dit?
This is fascinating. Now I'll stay awake all night, wondering if my real life happens when I'm asleep...
Very interesting post, but how are you going to resolve to have more restful sleep? It's not something one can control, is it?
I never make New Years Resolutions. I don't see why one should need something that only comes around once a year to make a change in one's life!
But perhaps I'm missing the point of your post. I did find it interesting!
We have similar resolutions. I have resolved to take more naps in 2008. Fascinating information, great writing.
IF: Haha! That happens to me too, sometimes. Resolutions aren't totally useless if you use them to fix the problems and not just the symptoms.
adamity: Erm, gee... thanks?
wendy: Too much sleep is also not a good thing - aim for the average, which is 7.5 uninterrupted hours every night.
claire: Luckily sleep paralysis is indeed strongly associated with adolescence, so hopefully it'll plague you less and less as time goes by. What I want to know is: how do you hook a dolphin up to an EEG machine?
morbidneko: And to you!
churchlady: Just don't read it right before bed...
aine: Birds also have NREM and REM sleep cycles - some even catch Z's on the wing! Once again, REM sleep has never been observed in reptiles.
jason: Thanks. It's a topic of immense fascination for me.
sonkind: Dit het nog nooit met my gebeur nie. Inteendeel, ek kry meeste van my beste idees in die stort!
lisa: That's a viable hypothesis, but how could we test it? Dream journals may help - and then there's the quagmire of lucid dreaming...
mike: Don't be silly - if you are neurologically healthy, of course there is! You must be sleep deprived if you missed 'the point' of the post, which is that sleep is a little-understood part of life that gets neglected way too often. As for the how: procrastination has a lot to do with it. It's also vital to keep a regular sleep schedule - don't sleep in over the weekend. Small afternoon powernaps of less than 30 minutes are also immensely beneficial in keeping you alert after dark. More than that and you do more harm than good, though. And countless other tricks I'm not going to share with you, 'cause it's all got to do with tryptophan, circadian rhythms and other technical things you indeed have a lot of control over.
angela: Thank you. You sound like a most sensible individual!
I have drawn blood in my nightime perigrinations and imbroglios.
I seem to relive crashes of the past. Fortunately these are quite infrequent.
Very cool cetacean info-WOW!
The great thing about learning is, and you hit upon it in many of your posts, is that it opens up worlds of other questions and querries. A "simple" look at sleep and suddenly many other ideas are interconnected.
I plan to get increase the quality of my sleep this year. My "sleep when you're dead" philosophy is a one way trip to disaster.
I see you have deleted your facebook account, so happy new year and all that jazz. Hope you are well! Chat soon.
Hehe, you misunderstood what I was getting at :) Nevermind!
Hope the resolution works out for you :)
wreckless: That's exactly it. On another note, perhaps if you strap yourself in you won't be such a violent sleeper? Thankfully you don't suffer from some of the other weird parasomnias like sleepeating or sexsomnia. At least, I hope not.
twanji: It is the road to ruin, for sure. And, I don't know what you're talking about.
mike: No, not nevermind, Mike, please inform me what you were getting at! You're the only blogger around here whom I seem to misunderstand with such alarming frequency.
Quite fascinating! DH experienced sleep paralysis years ago, and we've both wondered what that was.
I never thought about how sea creatures sleep. That was a fun read.
Thank you for this thought-provoking post! I enjoyed every word of it.
teoh: Another great post, Teoh. I can't stop thinking about the idea of completely depriving someone or something of sleep ... until it kills you. Can you imagine being kept awake for that many days? What would the death be like? Sounds like a Stephen King novel to me.
Sorry ... until it kills him/her/it.
church lady: It's one scary sleep abnormality that almost all of us have experienced, from people like my sister, to whom it happens every night of her life, to myself, who only experienced it once about eight years ago. The other abnormality is of course insomnia, but I doubt whether many people are scared by it.
sleekpelt: Ooh, you need to read an incredibly riveting, funny, scary and awesome book called The House of Sleep by Jonathan Coe. A small part of it is about exactly that...
Aw, well I don't want to be so misunderstood! I don't know what it is.
I guess what my comment was meant to say, was that, well, you start out on the theme of NY resolutions, and then state yours: to have more restful sleep.
But, the rest of the post is mostly informational on types of sleep, etc. And you don't really return to the theme of resolutions. It's quite easy to say 'I'm going to improve my quality of sleep', and while you might be able to do that by having regular sleeping patterns, etc (which you mention in your reply to my comment), how are you going to get the right balance of NREM and REM sleep?
So when i said I thought I might have missed the point, it was because in the comment I was blabbering on about NY resolutions when in fact your post was about sleep, not so much your resolution about getting more of a certain kind of it.
But, whatever. :)
G'day from Australia,
What a great resolution. I'd say sleep on it, but I think you've convinced me. Zzzzzzzzzzzz........
Oh, you always blow me away, with so much info, realife, twirled into a fairytale.....But here you have hit home, what about sleep flying? Paralysis in movement? Help me out here, friend!
Oh so interesting. I have a lot of strange ideas regarding the dreamstate. I like hearing about the scientific side, too, however.
im glad to pass by this place. very informative. you write so interestingly well, so fascinating.
Post a Comment