May 26, 2011

Evolution of Sleep

Ask a sleep researcher why we sleep, and s/he'll give you the simplest answer (which is sort of what scientists are all about): because we get sleepy. Can't really argue with that.

The next question is why do we get sleepy? There is a part of your brain called the suprachiasmatic nucleus (or SCN, for those of us who don't have time to pronounce that and/or have a stutter) that regulates your sleep schedule, and makes you get your sleepy on. I think mine is working a double shift today. It's noon, and I want to go to bed.

Someone with a normal SCN has a routine sleep cycle: the same amount of sleep around the same time each day, but someone with an impaired SCN (or a lab mouse whose SCN was destroyed, say) sleeps at random times for random durations.

The SCN sets your internal clock to a 25-hour day. Earth days, as you probably know, are 24 hours (ish--but I'm not going to go into that whole business). Sunlight recalibrates our SCN daily, so that we keep on track with the day length our planet has set for us. People in a sleep study who were kept indoors and weren't exposed to any natural light started deferring to their brains' 25-hour day.

There is a great variety of sleep behaviors in the animal kingdom, but nearly all animals exhibit some kind of sleep-like behavior. Even sponges slow down at night, although it's not clear whether or not that constitutes sleep.

Sleep was obviously advantageous for our flashlight-less ancestors, as it kept them from stumbling around in the dark, getting eaten by lions or falling down bottomless pits. But it still seems like such a massive disadvantage to be unconscious and vulnerable for a third of the day.

But it's not all about staying safe when it's dark; after all, animals that have great night vision have to sleep, too. As I explained earlier, sleep is very important for the brain--the more complex the creature's brain, the more serious the sleep.

To make sleep yet more confusing and weird, scientists discovered that blind cave fish get by on almost no sleep at all. Maybe they evolved to need less sleep because their environment requires them to constantly be on the search for food, but I also read that this suggests that part of sleep's purpose is to process the visual input collected during waking hours. So no input, no need to process. But of course, blind humans still need sleep, so don't go and blindfold yourself so that you won't have to sleep. 'Twon't work.

Brainy aquatic species like dolphins and whales still need their sleep, and their situation is a difficult one. How do you find a safe place to sleep in the open ocean and refrain from drowning while you do it? The answer is unihemispheric sleep--sleeping half a brain at a time. The other half can keep an eye out for danger and make sure the animal breathes.

Thus endeth the Beatrice Sleep Post Trilogy--my poor attempt to explain one of the most mysterious, complex, and yet totally familiar science topics, where what we know hardly compares to what we don't know.

I'll leave you with what my sleep research source told me when I asked a million questions about why we must sleep:
"If sleep were not important then it is probably the most significant mistake, evolutionary speaking, ever made."
Well, that and hairless rodents. Yeesh.

May 19, 2011

While You Were Sleeping

Sleep is a state of being in which the individual is relatively unresponsive to external stimuli, typically with eyelids closed, in a supine postural position. This activity has a certain periodicity during a 24 period.

Translation: When you sleep, you're totally out of it and probably lying down, and you do it around the same time everyday. Yes, this could just as accurately describe a daily bubble bath, but just deal with it. I don't have time for this.

Very helpful pictorial representation:

Sleep seems like a relatively passive, lazy experience, but that is far from the truth. There is a whole lot going on.

While you sleep, your brain goes through cycles of 5 phases: phase 1, phase 2, phase 3, phase 4, and REM (rapid eye movement).

Each complete cycle lasts about 90 minutes.

A very basic representation of a few sleep cycles. 
But I wouldn't put this in a textbook or anything. 
It looks pretty awful. 

Phase 4 is the deepest, most restorative sleep. It's in this phase that your cells engage in protein synthesis and repair themselves. Why don't they do it while we're awake? I guess we're not good multitaskers. Deep sleep is a time for cellular housekeeping, since our body doesn't have to tend to our waking needs like moving and whining.

During REM sleep, your brain is more active than it is when you're awake. REM is important for brain development and maintaining neural connections you've made while you're awake, which is why sleep is so important for your memory. Infants' developing brains spend 50% of their sleep in REM, while adults spend just 24% of their sleep there.

REM sleep is quite famous because it's where dreams happen (but never come true! Bwahahaha). To protect you from yourself, the brain shuts off the spinal cord during REM sleep so that you can't punch yourself while you dream about fighting off those ninjas. When there is an error in this step, you get your really fun sleep walking or night terror incidents. I've sleepwalked (sleptwalked?) a few times in my life. One of those times involved my sleepwalking crazyface ripping the covers off the bed and telling my then boyfriend (current husband) that a little boy in the living room asked me to bring him the blanket. I don't recommend doing this to anyone. They really don't like it.

If you wake up during this REM-induced paralysis, you can experience sleep paralysis awfulness. I've never woken up this way (because my REM paralysis doesn't work so well--see above), but I've heard it's rather terrible.

Superstitious people of yore were particularly disturbed by sleep paralysis and came up with some convincing explanations. They imagined an Old Hag whose spirit would come and sit on your chest, leaving you breathless and motionless when you woke up. The term nightmare originally described this feeling of sleep paralysis, not bad dreams like it does today.

If you wake up when you're in light sleep (stages 1 and 2), you wake up feeling refreshed and shiny, but if your alarm goes off when you're in deep sleep, you're a groggy mess. Since the sleep cycle is about 90 minutes long, apparently some people try to set their alarm for a multiple of 90 minutes after they go to sleep, in the hopes of waking up from lighter sleep. I'm way too lazy to do that, but I probably should. My alarm and I don't have the best relationship.

The sleep phenomenon that science has yet to tackle is why any kind of baby is cute when it's asleep, especially when it's in an inappropriate place.

During my research for some funny pictures of people/animals sleeping, I discovered that these domain names are mysteriously unclaimed. Investment opportunity!

But this one is taken, and definitely worth a look:

May 17, 2011

Sleep Deprivation

I just got back from a 2-week trip to Thailand. While I was there, I never achieved more than 6 hours of sleep per night (as there was plenty to do besides sleep), and on the way back, I experienced a level of sleep deprivation I have never known before.

Maybe you're one of those supermutants that pulls all-nighters with ease or can sleep on planes, but I've never pulled an all-nighter in my life, and to sleep on a plane I'd need someone to pistol whip me out of consciousness, and alas pistols aren't allowed on planes these days.

This 54 hour bout of sleeplessness (minus a nap during a layover) eventually robbed me of all my faculties.

So let's talk about this mysterious requirement that I have, that we all have, and what can happen when we don't get enough of it.

Even though we spend a third of our lives engaged in this activity,

we know surprisingly little about sleep. But what we do know is that it's really super awesome. For our brain, it's important for memory and attention, as well as neural development (which is why babies do so much of it). For the rest of the body, sleep is a time that cells do protein synthesis and repair themselves, including immune cells. That's why getting ample sleep is a great way to avoid getting sick.

We know that people who consistently get less than 6 hours of sleep per night are at risk to develop a whole basket of health problems: cadiovascular disease, hypertension, diabetes, obesity. Because of the fatigue, sleep-impaired people are more likely to be involved in car or work-related accidents. Studies show that the overall cost of healthcare for sleep-challenged individuals is significantly higher than the cost for their sleeping friends.

But don't try to be a sleep overachiever, either. Studies show that there is a definite bell curve. Too little is definitely not good, but too much sleep is just as bad. People who habitually get more than 9 hours per night have some of the same health risks as insomniacs.

I'm going to rethink my adoration of my weekend ritual of amassing 10 hours of sleep per night.

However, there are people who are true "short sleepers." They can get less than 6 hours per night and do not develop any negative symptoms. Good for them. Those showoffs.

It seems the Guinness Book of World Records doesn't currently have an entry for "longest bout without sleep," but a past record set by Randy Gardner was 264 hours, or 11 days. I certainly won't be the one to upstage him.

You will indeed die without sleep, but luckily your body simply won't allow you to do this. Our bodies are pretty talented at getting what they want. If we continually don't allow ourselves to sleep, eventually the body gives us no choice. Just like in the new Freddy Krueger movie, if you force yourself to stay up long enough, you experience microsleeps, in which the brain electrophysiologically enters a sleep like state, whether you like it or not. I imagine that someone engaging in microsleep resembles me on a Monday.

For several (obvious) reasons, there are no extreme sleep deprivation studies with humans as subjects, but there are some with mice. A mouse lasts about 30 days without sleep and then dies, but there isn't consensus on the actual cause of death. Does the brain shut down first? Or the heart? Or is it just across the board failure? The scientists who did this study also noted that the mice experienced a shutdown in thermoregulation: their body temperature became completely unstable. Poor little mice.

Since sleep is a complicated brain ballet, there are of course several disorders associated with it. Narcolepsy is a well-known one, in which sufferers fall asleep suddenly. But a lesser known breakdown in the sleep cycle is fatal familial insomnia. The name says it all.

FFI isn't any kind of regular ol' I-can't-sleep insomnia. It's a prion disease that affects the thalamus, and eventually the brain becomes completely unable to enter a sleep state. But unlike mad cow and other prion diseases (which I discuss in a past post), this prion disorder is genetic. About 40 families and 100 individuals suffer from this disorder worldwide. Onset is usually later in life (around age 50), and the disease lasts about 18 months (depending on the person), with ever-increasing difficulty sleeping, progressing to complete insomnia that eventually causes hallucinations, dementia, coma, and death.

I feel like this is where I should make a joke to lighten the mood, and yet I feel as though my hands are tied.

So now I feel like my 54 hours without sleep perhaps wasn't so bad, and I'm looking forward to sleeping tonight and fully appreciating it's awesomeness.

A special thank you to Professor Wincor for taking the time to discuss sleep deprivation with me. I have 3 upcoming posts about other parts of our discussion. I'm very grateful for your help!

May 14, 2011

Missing Sleep Deprivation Post

I'm sorry if you were trying to find my post on sleep deprivation. Blogger experienced a system-wide error that resulted in the temporary loss of posts that were published on May 11th and 12th. Unfortunately, my post was included in this. It will hopefully be back up soon. Sorry for any confusion.


May 06, 2011

Winner of Beatrice Giveaway Numero Deux

The moment is upon us!















Thank you to everyone who entered! There will be another giveaway soon!