Sunday, August 28, 2005

Of Optical Illusions, Kinetics and ADHD

An alert reader has put us onto a website that has 57 optical illusions:
It is pretty awesome and I confess I haven't been through the whole thing, but I will. It brings up some interesting things that wander through one's cerebrosphere late it night when the crickets are singing. You need to click on the "rotating snakes" from this website below to see it better.

Optical illusions are interesting because they tell us something about consciousness. (!) Some of the recent work has shown that that cinema that plays in our head on a constant basis and, probably, when we’re asleep but we have our eyes shut (yuk, yuk), is not a continuous flow as we experience. It is actually like real cinema in that the brain assembles an optical (and I assume auditory and other sensual experience) “shot” at set time intervals. The time interval is short enough that we experience it as continuous reality. There are some unfortunate people where this doesn’t work and their experience “stutters.” Must be discomforting. On the other hand, some people have nystagmus. If you have them follow a light across their eyes, the eyes do not move smoothly across, they stutter. Interestingly enough, their visual experience doesn’t stutter. We have an amazing brain. There are even some children with rotary nystagmus. Imagine the high speed computing that goes into presenting a coherent and stationary image to the brain where the eyes are doing cartwheels!

The most interesting thing about all this relates to an underlying problem that I have been thinking about for years, the role of enzyme kinetics. Consider an organism for the moment, say something simple like a single cell bacterium (even this is complicated beyond our ability to understand). Contained within the tiny cell is an enormous number of chemical reactions all taking place at the same time. There is the energy metabolism, there is the synthesis of proteins and lipids, and there is the entire, separate mechanism of reproduction. Almost every single step in the bacteria’s metabolism is catalyzed by an enzyme, itself a protein. While every single reaction would itself go to equilibrium if left to itself, some of these reactions would take years, thus the necessity of the enzyme catalyst. Enzymes, to use the metaphor, make the playing field level. Actually, they don’t make it level, they make it consistent. By that I mean that they adjust the rate of each reaction so it exactly fits into the multiple competing reactions and makes the damn thing go. Amazing.

One can view cellular DNA, which is contained in all organisms except a few, nasty viri, as “mapping” a set of rate constants on the corresponding set of reactions. Our goal should be to sort out these rates. In particular, as in any series of chemical reactions, we should try and discover the “rate limiting step.” I can think of a number of disease where this might be of interest, including the multiple diseases under the rubric Cancer. But this is for a later day.

What of interest here is that the video that plays across our consciousness is most likely a staccato performance (though perceived as smooth, as discussed above) because the neural chemistry is rate limited at one or more step. What that step is I haven’t a clue though I would look closely at the synthesis of neurotransmitters. I suspect that the electrical side of the process, i.e. axonal transmission via the action potential, is pretty rapid (though it does depend on ion movement and pumping).

This brings up a number of questions including evolution. Have we reached the end of evolution for the human brain because we have reached the chemical limit of thought? If the neurotransmitter synthesis enzymes in our brain were “speeded up” by mutations would we think faster? Would we evolve to the next level (unknown in the same way that prehomids could not conceive of Beethoven’s piano sonatas)? Does the current epidemic of methamphetamine abuse, which clearly speeds up thinking as it does for people with Attention Deficit Hyperactivity disorder, represent the craving of the human brain for this next level?

Stay tuned!


Dr. C said...

Hey RJ, why'd you block comments on your blog?

Redjalapeno said...

I didn't mean to!!

Everything is back to normal, for now.