I just went for a drive under the influence. Of what, I'm not sure.
I was sitting at my keyboard, following a few IRC channels and testing a build of some code, when suddenly I noticed that everything seemed to be moving very quickly and very slowly at the same time. I became aware of my typing: my fingers were moving at breakneck speed, it seemed, flying over the keys faster than should be humanly possible. At the same time, I was calmly conscious of what I was typing, and the words seemed to be proceeding from my fingers at a stately pace. Every motion I made was accompanied by the same contradictory twin senses: that the movement was wildly fast and serenely slow at the same time.
This is far from the first time that I've noticed this happen. It's been happening since I was a teenager at least. This is the first time in months, possibly a year. Once or twice a year, throughout my lifetime, is probably a good estimate.
It starts without warning. The only effect is that my perception of speed changes, or maybe disappears, leaving me with the feeling that everything is happening too quickly and too slowly. Noises seem louder as well. This time, for example, the refrigerator motor was running and it, along with my normal collection of computer fans, was very noticeable. I haven't noticed any alterations in vision or any other senses.
In general there is a heightened sense of perception, though this is likely just because I am curious about the phenomenon and am actively paying attention to my surroundings.
The twin sensations of speed and slowness are somewhat different in character. The feeling of speed is a kind of excitedness and rush, minus adrenaline. The closest I've felt to it in everyday life is when I played soccer or table-tennis: the feeling was similar to the focus when someone with the soccer ball was rushing me and I had to stop them, or when I was in the zone and volleying over the net just at the edge of my ability. With this, there's no emotional involvement, no excitement, just the awareness that "this is happening a bit faster than I can deal with," or perhaps more precisely: "geez, look at that go!" or "look at me go!"
But the feeling of slowness is more like being surprised that "this is still going on?" We plan our everyday activities one thing at a time: first I'll walk over there, then I'll turn on the light, then I'll pick up the pen, then I'll... etc. The feeling of slowness is a feeling that the current action is taking longer than expected to get through. "Aren't we done with this yet?"
When this happens, normally I just... well, keep doing whatever I'm doing. I can function quite normally, my consciousness, judgement, and coding skills are quite unimpaired -- it just feels strange. This time I wanted to try something new. I got my keys (loud frenetic jangling), walked outside, locked the door (swift latching), walked to the car like I was an actor in a sped-up movie, climbed in, started it up and pulled out.
I was very cautious of course. I definitely got a feeling of fast movement even from trundling forward in first gear. When I pulled up to the exit gate, it seemed to rise very quickly, while taking forever to do so.
Once I got out of first gear and on the road, I found something very interesting. I could experience either the feeling of moving very swiftly, or the feeling of standing almost still, depending on which I wanted to focus on. When I noted how swiftly I was moving, as I did at first, the car's acceleration seemed instantaneous: I barely was in one gear before it was time for the next, and the trees just flew by.
And then, a moment later, when I decided to pay attention to how slowly it was all happening, the car seemed to be hardly moving at all. That was even stranger: I had to look down at the speedometer to note my speed (45MPH) -- and when I looked back up, it felt like I was in a go-kart trundling slowly along. If I hadn't known better I would have sworn I was doing 10MPH.
I braked early for the stoplight just to be on the safe side. Despite the odd sensations, or maybe because I was being incredibly careful, I had no real problems driving.
After I turned, I decided I wanted to take the top down (it's a hot day today). I pulled into a parking lot and somehow sensed the feeling was subsiding. As I unzipped the rear window and pulled the top down, those actions felt more normal than usual. By the time I turned around and pulled back onto the road, it was gone; all was right again. Time since the stoplight was about 15 seconds. Total elapsed time of this sensation, from typing to putting the top down, was probably three to four minutes.
For the record, I don't do drugs, I don't smoke, I don't drink, and I haven't for over ten years. The only drug in my system at the time was one cup of half-caf coffee I'd drunk six hours earlier, and 47 grams of sugar from a can of non-caf soda. I'd eaten a nice lunch a few hours before, so my blood sugar was relatively stable. I notice I'm getting a bit of a headache now, but that happens frequently anyway. Nothing I've eaten or imbibed today has been unusual in any way.
In other instances of this phenomenon, I've noticed that my sensation of size has changed as well. My fingers, in particular, will feel both daintily tiny and grossly large. I didn't pay attention to that aspect of it today, but I'm sure if I had, I would have noticed it again.
My hypothesis is that there is some portion of the brain that regulates perception of time. Our brains are quite well equipped to expect things to happen at a precise time: we can jump off a small ledge, close our eyes halfway down, and know intuitively when to flex our knees for the landing. Somehow this part of my brain goes on the fritz, or becomes disconnected, twice a year. What I perceive as simultaneously "too fast" and "too slow" is, I believe, how my consciousness interprets lack of the "this looks normal" message from lower in the brain. In essence, my forebrain asks my mid- or hindbrain, "does the proportion/speed of this look 'normal'?" When the answer fails to come back in some appropriate way, any explanation I want will do: an object will be too large if I want it to be, or too small, or things will be happening too fast, or too slow. Without the reassurance of correctness, apparently, my consciousness will accept any explanation as valid.
But -- nothing I've read about the brain has mentioned any such structure. And, not being a brain surgeon, I'm not exactly in a position to test my hypothesis. Oh well.
I have to wonder if anyone has ever had this same experience. And I wonder whether others, having a similar experience, and knowing nothing of the way the brain works, have called it "leaving their body" or "a fugue state." I could easily see blaming demons -- but me, I just think it's cool.
Followup, September 15:
After I wrote the above, Scientific American's September 2002 issue came out. Its focus is on time. On pp. 59-65 is a fascinating look at how the brain measures time.
"The interval timer helps you figure out how fast you have to run to catch a baseball. It tells you when to clap to your favorite song. It lets you sense how long you can lounge in bed after the alarm goes off."
The theory described in the article is that spiny neurons in the striatum are essentially oscillators, firing 10 to 40 times a second, and that interval-timing involves synching them up and then watching for patterns. Interesting stuff.
I don't think a fault in this system is what was wrong with me. I recognize that interval-timing might be used at a variety of levels, but I doubt it could also explain the difference in my perception of dimensions.
Followup, January 23, 2006:
I think it's only happened once since 2002, by the way.
I just read this passage from "How Meditation Works" and was struck by the similarity of the physical awareness described here with the experience I occasionally undergo involuntarily. The description of body parts gaining or losing size and weight is dead-on, and I couldn't have phrased this better myself: "Each component of the event seems to contain vast expanses of time and space within which to perceive information in an unhurried way." Also, footnote 14.
And increased awareness and clarity is indeed part of the experience: I feel as if every scrap of sound, every individual action and sub-action, everything within my sphere of senses is specifically discernable. Or, of course, seems to be -- since it's my brain doing this, how would I know whether I actually have increased awareness or just the illusion of it?
Anyway, the final paragraph below describes using (a similar or identical?) meditational experience of events as a metaphor (or tool?) to explore one's thoughts and sub-thoughts, "emotions, concepts and mental images" in the same way. That would be interesting, but not interesting enough for me to invest untold hours meditating. As for the physical experience I occasionally undergo: again, interesting, but not life-changing. Really not that much of a payoff. I've always thought of it as my brain briefly breaking somehow, and then fixing itself. Never considered trying to live my whole life that way. Whatever floats your boat...
A common approach used in the Theravada tradition is to flood the consciousness with more and more complete and precise information about mental and physical events. Typically, one first learns to experience this intense "vipashyana mode" of observation for a single simple event. Once learned, this can be generalized and applied to any aspect of experience. With practice, a habitual suppleness is developed which allows one to perceive each event in the stream of daily life in this totally aware way without having to work at it.
Take, for example, the act of walking. Most people do it unconsciously. There's nothing wrong with that, but suppose you would like to enhance awareness of this event "walking." You could start by mentally noting which foot is swinging at any particular time. This gives you a tiny bit more information about the reality of walking than doing it unconsciously. Next, with regard to each foot, try to note the very instant when the foot begins to rise and the instant when it again touches the ground.  Left up, left swing, left down, right up, right swing, right... For still more detailed observation, it is useful at the beginning to walk much more slowly than normal and perhaps to pause between each component of the walking. Now, note the instant the left heel rises, note the sweep of tactile sensation as the sole lifts away from the ground. Note the moment the toes leave the ground, the beginning of the forward swing, the swing itself, the end point of the swing, the beginning of lowering the foot, the lowering, the instant the foot touches ground, again the sweep of tactile sensation and the instant when the foot has completely returned to the ground. Now pause. Note when the will to move the right foot arises. Now begin to move the right foot, observing each component as before.
Such an exercise builds much samadhi, but this is a byproduct. The important thing is increased clarity about the process. After more practice, it is possible to apply an even finer analysis. Within each component of the motion (lifting, swinging, lowering, etc.) can be distinguished numerous subcomponents, tiny jerks each with distinct beginning and end points and each preceded by a separate will to move. If this keen observation is sustained, alterations in perception begin to occur. The event seems to slow down, a subjective sensation independent of any actual physical slowness. Each component of the event seems to contain vast expanses of time and space within which to perceive information in an unhurried way. 
But wait. As your information about the foot gets fuller and fuller, the foot seems to be less and less there! It expands, contracts, becomes light and hollow, merges with things, disappears and reappears. Without being seduced or frightened, just keep on noting the simple reality of the foots moment-to-moment motion.
This "vipashyana mode" of awareness can be applied to every type of experience. One can gently move the eye over an object, drinking in information about it so rapidly and fully that the consciousness has no time to solidify and limit the object. Likewise with other senses, touch, taste, smell, hearing, etc. This is the fundamental paradox of meditation: see something fully and it is transparent, hear fully and there is silence. The feeling of solidity and separateness of objects, which most people take for granted, turns out to be merely an unnecessary and toxic byproduct of the process of perception. It clogs the flowing stream of life. One can function quite well without it.
Applying this total mode of awareness to emotions, concepts and mental images is the most difficult but most productive exercise of all. The stream of a person's thoughts and feelings is so unpredictable and gripping
... not at all like raising and lowering a foot! Yet with the detachment and one-pointedness of shamatha, one can catch a thought at its very onset and note each minute permutation until the very end in that same slowed down, complete, unsolidified mode of awareness. A person who can unrelentingly apply this mode to his or her deepest images of self will enter a refreshing new world.
13. In attempting to fully experience any event, it is of utmost importance that the event's beginning and ending points be clearly noted. A line segment which includes its first and last point is mathematically very different from one which does not. Return
14. John Brodie, former quarterback of the San Francisco 49ers, recalled such experiences in an interview published in the January 1973 issue of intellectual Digest (pp 19-20):
"At times, and with increasing frequency now, I experience a kind of clarity that I've never seen adequately described in a football story. Sometimes, for example, time seems to slow way down, in an uncanny way, as if everyone were moving in slow motion. It seems as if I have all the time in the world to watch the receivers run their patterns, and yet I know the defensive line is coming at me just as fast as ever. I know perfectly well how hard and fast those guys are coming and yet the whole thing seems like a movie or a dance in slow motion. It's beautiful."