On Sleep

I think it’s pretty common to think of how asleep someone is as something that comes in degrees, by which I mean that someone can be a little bit asleep (in which case their eyes will be closed, but they might remember overhearing a conversation nearby, and be wake-able with very little stimulus, such as someone whispering their name, or opening the door of the room they are in), or very very deeply asleep, in which case they might sleep through a loud storm/band playing next door/someone poking them or even moving them, and in all kinds of states in between. But Demmett and Vaughan’s The Promise of Sleep argues that this is wrong: though there are indeed different kinds of sleep (i.e. stages 1-4 and REM sleep) sleep itself is discrete on/off thing.

The main experiment Demmett cites in support of this goes more or less like this: you keep a subject awake for 3 or 4 days, so that they build up a large sleep debt, making them liable to fall asleep quickly. Then you clip their eyelids open (yes, it does sound torturous) and sit them in front of a bright flash, like that of a camera, which goes of randomly, but on average every 8 seconds or so. Then you ask them to push a button every time the flash goes off. Here’s what happens. For the first couple of minutes they push the button diligently every time the flash goes off. But after a couple of minutes, there is a flash and they fail to push the button. The experimenters ask them why they didn’t push the button, and the subject replies that there was no flash. But of course, there was a flash, the experimenters all saw it, and the subject is sitting there with their eyes pinned open in front of the flash bulb. The electrodes attached to the subject’s scalp (which you can use to measure electrical activity in the brain) show that the subject actually fell asleep for 2 seconds.

Demmett argues that sleep is total cut-off of normal perceptual processes: basically the brain drops a wall between the subject and the outside world, such that the sleeper simply doesn’t perceive the outside world at all. The difference between sleep and unconsciousness, coma or death is that certain things can prompt the removal of the wall (sounds, shaking the sleeper, etc). But still, either the wall is there or it isn’t—-the subject is either asleep or he isn’t—-and if he’s capable of paying attention to anything in the outer world (groggily attending to nearby conversations, for example, or some language learning tape) then he isn’t asleep at all.All of which makes sleep seem really strange.

It’s clear from the book that nearly everything we know about sleep has been discovered very recently, and that a lot of falsehoods about sleep are still very widespread. Some of the new data about sleep has been achieved-unsurprisingly enough-through new ways of studying the brain, but there’s also been plenty discovered that could have been discovered much earlier if only someone had looked. In fact, it’s completely amazing, and in need of explanation, that no-one every noticed these things before. For example, Rapid Eye Movement (REM) during sleep is strikingly obvious to anyone who’d care to look. And it is ubiquitous: everyone – babies, old people, animals, men, women – has hours of REM sleep every night (well, in the case of nocturnal animals, it might be during the day, and hibernation and the like turn out to be special cases. And it takes a few weeks before the sleep of babies is consolidated into longish alternating periods of wake and sleep..but you get the point – REM sleep is all over the place.) And it isn’t as if no-one ever watched anyone else sleep. And yet pre-20th century theories of sleep (Aristotle apparently thought vapours arising from one’s stomach after eating put one to sleep) make no mention of it, and it wasn’t discovered and studied until a few years ago. Why?Is it just that people assumed sleep was uninteresting?

It seems to me that there are a bunch of issues that could be of interest to philosophers here, but the only philosophy of sleep book I’ve found on Amazon is Robert Macnish’s The Philosophy Of Sleep, which is a 2006 reprint of the 1830 book. Here’s his description of waking from a healthy night’s sleep:

The sleep of health is full of tranquility. In such a state we remain for hours at a time in unbroken repose, nature banqueting on its sweets, renewing its lost energies, and laying in a fresh store for the succeeding day. This accomplished, the slumber vanishes like a vapour before the rising sun; languor has been succeeded by strength; and all the faculties, mental and corporeal, are recruited. In this delightful state, man assimilates most with that in which Adam sprang from his creator’s hands, fresh, buoyant and vigourous; rejoicing as a racer to run his course, with all its appetencies of enjoyment on the edge, and all his feelings and faculties prepared for exertion. (2) 

So, no need for coffee then! And no beta-waves. There is some mention of eye movement in the index, so I’m going to order a copy of the book (I got this stuff from the Amazon “search inside” feature) and see if there’s anything that could be construed as early observation of REM. There might be a few more posts about sleep in the next few days or so.

5 Replies to “On Sleep”

  1. I don’t know, the book only mentions it in passing and remarks that it was a commonly accepted theory until it was realised that it was anatomically impossible.

    But I can imagine people thinking that the theory accounts for the fact that it is hard to go to sleep when you’re hungry, and easy to go to sleep if you’ve overeaten. Then they can set about explaining any apparent exceptions in terms of interference with the vapour mechanism.

  2. One area of philosophical interest is the standing information to which we have access both when awake and when asleep. I take it that if I dream of a city in which there is a big art gallery, containing a painting labelled “Mona Lisa”, my dream is about the real Paris, just as my waking thoughts about a city like that are about the real Paris. (If you think that dreams are not about real things at all, please stop here.)

    If it is true that subject matter of my dream is the real Paris, it must be because standing information about real cities is in some sense available behind the sleep wall. (The information could be images or propositional content.) The scope for dreamers to imagine all sorts of cities, some bizarre, some very close to actual cities, makes a purely descriptive theory of reference particularly unattractive when working through the wall, even if it might work when we were awake (although I don’t think it would). So I think that we need some sort of link to the outside world. If the wall blocks occurrent input from the real world then the standing information, derived when awake from direct or secondhand experience of the real world, seems to be the only option.

    In what sense need the standing information be available? It seems that it would be enough for my dream to have had its apparent content (the pseudo-sensory impressions) because of that standing information, in a neuronal-causal sense of “because”. I have impressions derived from the real Paris in my database of standing information, so images like the impressions one gets from being in the real Paris can easily pop into my head when I am dreaming.

    If the standing information only has to be available in that sense, rather than being consciously consulted in the dream, then we do not get an easy way to distinguish dreaming from waking. If the standing information had to be available for conscious consultation, we might well notice that we were getting pseudo-sensory impressions of places which were not covered by our standing information, and therefore work out that these were imaginary places, demonstrating that we were dreaming (or perhaps that the places were real but that the related information had slipped out of our consciously accessible database).

    I have been using standing information to trace a causal chain from the real Paris, through the wall of sleep, to a dream. So to what extent can a dream be about Paris even if it includes pseudo-sensory impressions which are not ones that someone would receive in the real Paris? A little latitude should surely be allowed. Even if you ask me to think about Paris when awake, I will make some mistakes, but I am still thinking about Paris. But it is harder to say how much latitude should be allowed with dreamers than it is with the awake, because the dreaming process is so undisciplined. A dream can very easily be inspired by mixtures of images of Paris and Berlin in various proportions. And to what extent is a dream still linked to the real world by its derivation from images from the database of standing information when those images are heavily distorted, as often happens in dreams but much more rarely in waking life? Am I still making a connection with the real Paris when in my dream, the Mona Lisa is a hologram racing out of the Louvre to catch the last metro?

    And so to bed …

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