Doggedly searching for the crux of the biscuit.
I mean really look at them?
Preposterous Universe has the most interesting post I've read in some time. In the 20s and 30s, Heinrich Kluever established four basic classes of hallucinations: spirals, spokes, honeycombs, and cobwebs. If your college years resembled mine, those should ring a bell. We are now discovering that these patterns occur for a specific reason, and expressed mathematically, that reason is roughly:
da(x,φ,t)/dt = -a(x,φ,t) + I(x,φ,t) + ∫ dx' dφ' f(x-x',φ-φ')a(x',φ',t)
Got that? The technical details are likely to make your eyes glaze over and possibly induce a few spirals or spokes, but here's the short version.
Okay, the previous paragraph may or may not have made any sense to you. But here is the punchline: patterns of hallucinations reflect normal modes of the neurons in the visual cortex. By "normal modes" we mean the characteristic patterns of vibration, just as for a violin string or the head of a drum. The idea is that a drug such as LSD can alter the ground state of the visual cortex, so that it becomes excited even in the absence of stimuli. In particular, certain oscillating patterns can appear spontaneously. Generally these would take the form of different configurations of straight lines in the cortex itself; however, due to the distortion in the map from our visual field to the brain, these appear to us as spirals, tunnels, and so on. Indeed, Cowan and collaborators have shown that these normal modes can successfully account for all of the basic forms of hallucination classified by Kluever decades ago.
So, the next time you have a near-death experience, and see a tunnel stretching before you leading to a beckoning light, it's not Jesus calling you into the afterlife. It's just some characteristic jiggling of the neurons in your weakened brain. Which, to my mind, is much more interesting.
(via the new-look Poor Man)
TrackBackSquint your eyes and stare at that equation for a while.
Did you see Jimi?
Use your thumb to cover the I(x,φ,t) term.
Yeah, me too...
Antidisestablishmentarianism
Yeah, I'm a bit at a loss why anybody should (outside of university circles) want to show us that absurd equation. It may mean something to somebody, but to 99.9999% of us... nothing.
I think it has something to do with someone (not here) being really excited that he could produce all those symbols on a computer...
No offense, cause you were if anything poking fun at it, but it's very much like a latin tag. People are supposed to be very impressed that you can quote latin, when the truth is that you can copy a latin tag...
Posted by: Ryan at February 5, 2005 08:55 PMI'm impressed with anyone that remembers what any equations mean, past age 23 or so. So few of them really prove necessary for us each day. I look at some of my old chemistry or physics papers and think: wow, I wrote that?
Nemo perscribo? Okay. ;)
Posted by: Ru at February 6, 2005 12:51 AMI hardly remember β=X(X′X)¯¹X′Y, even though I use that most every day.
Posted by: John Johnson at February 6, 2005 10:44 AMHey, a-man? Where does "did you ever really look at your hands?" come from? I remember it from an old Doonesbury cartoon, but surely it has some other source...
Posted by: FL at February 7, 2005 12:32 AMAwww, c'mon guys. If you read the linked article the equation is not that bad. The real good stuff is hidden in the ∫ dx' dφ' f(x-x',φ-φ')a(x',φ',t).
I think this is great! I've always been fascinated with vision and pattern recognition. I was diagnosed with glaucoma at the age of 21, which made me very aware of the eyesight I had. With treatment I've had no loss of vision (and NO medical MJ) so far.
I can't say I've ever had drug visions, but once I did have a migraine vision. It was a single, glowing, curved line that slowly swept across my field of vision, taking about 10 minutes. My guess, now, is that it may have been a straight line in the visual cortex that moved across the neurons.
You know what these guys should do? Write a program so that you could mark up a virtual video cortex and see what the vision would appear like. That would be really, really cool!
Posted by: Tripp at February 7, 2005 10:26 AMI agree that the equation is not complicated, but I get why many find them intimidating. I think a good analogy is sheet music. You need a tiny bit of background in the symbols before you can make sense out of it.
Tripp- Migraine auras are amazing! This article does seem to explain their patterns, too. Of course, they are often followed by pain, and the first time you have one you find yourself a bit stunned. But once you know what it means, it is an interesting experience. For migraine sufferers they are also unmistakable warning signs that allow time to get medicated and possibly prevent the rest of the symptoms.
Posted by: Ru at February 7, 2005 02:30 PMRu,
Luckily, I had the aura only once, and have never had a migraine. My opthamologist diagnosed it.
Posted by: Tripp at February 7, 2005 02:46 PMI agree that the equation is not complicated, but I get why many find them intimidating.
Intimidating my ass. If I post a piece of French poetry on my site... for exammple:
Vienne la nuit sonne l'heure
Les jours s'en vont je demeure
and I don't produce a translation (which I don't) I can expect people (and I don't care) to tune out. I can't expect the above mathematical quotation to be any more simple than "Comes the night which tolls the time, The days will pass but I remain..."
Geeks frolic in techy speak. Get over it.
Thankssoverymuchforthisgreatwebsite.AlexanderSchmitz.f939fjwkwqllq.
Posted by: AlexanderSchmitz at February 9, 2005 06:18 PM