From: J. R. Molloy (jr@shasta.com)
Date: Sun Apr 01 2001 - 14:58:39 MDT
From: "Anders Sandberg" <asa@nada.kth.se>
> There is currently a big debate among us neuroscience people about
> rate coding vs. spike coding. Neurons in mammals usually send signals
> by action potentials, quick voltage spikes that cause synapses to
> transmit the signal to the recipient neurons. This is highly digital
> in itself, although various nonlinearities in the system make it
> possible that the interval between spikes might matter for some
> processes.
Then time may act as an analog influence on human (mammalian) cognition?
> The rate coding view thinks that what really matters is
> just the average rate of firing, while the spike coding view thinks
> that it is the intervals that matter. The truth is likely somewhere in
> between; there are evidence for several forms of coding in various
> parts of the system. Some neurons appear to prefer an on/off approach
> to activity, either being silent or firing away at a high rate, while
> others are more gradual in their responses or show complex
> interactions. Personally I tend to lean towards the rate position more
> than the spike position, but things are not clear cut or simple.
It sounds to me like the brain forms its operating modus from
utility/opportunity rather than from prescription. IOW, whatever gets the job
done, works well enough.
> In any case, different codes are limited by the noise levels in the
> system which appear to be fairly high. Synapses sometimes accidentally
> release vesicles, neurons sometimes misfire or do not fire when they
> should, cells die etc. I would say the human brain is a largely
> digital system employing special purpose analog components; the analog
> parts do not have direct contact with each other, so whatever analog
> information is around either exists as spike timing or possibly
> chemical gradients. But as I said, it is all noisy.
These analog components sound like they're related to senses, yes? Does the
sense of time (that humans experience subjectively) constitute an analog
function? Perhaps it would help to define "analog components" in terms of
quantum physics. Or perhaps not. (?) Anyway, can we find an example of
something that is truly analog, as opposed to what we find in the real world
of discrete objects and quantified materials?
Stay hungry,
--J. R.
Useless hypotheses:
consciousness, phlogiston, philosophy, vitalism, mind, free will, qualia,
analog computing
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