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Article 7553 of comp.ai.philosophy:
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>From: biesel@javelin.sim.es.com (Heiner Biesel)
Subject: Re: Human vs. Machine
Message-ID: <BxGqqu.Auu@javelin.sim.es.com>
Organization: Evans & Sutherland Computer Corp.
References: <1992Nov2.171938.604@cine88.cineca.it>
Date: Mon, 9 Nov 1992 19:13:41 GMT
Lines: 45

>In article <1992Oct19.210541.21740@news.media.mit.edu>
>minsky@media.mit.edu (Marvin Minsky) writes:
>> [...]
>>Why do you assume that the brain is singularly unpredictable, or that
>>there is an fundamental problem is assessing the properties of all the
>>synapses in, say, your brain?  Consider the location of anything so large as a
>>neurotransmitter vesicle.  (In some theories of synaptic thresholds,
>>the number of these is a critical parameter.)  The heisenberg
>>uncertainty of that location is many orders of magnitude smaller than
>>its thermodynamic variance; in effect, Heisenberg uncertainty probably
>>is irrelevant to neurological performance.
>>
>>The thermodynamic chaotic aspect is somewhat more relevant, but there
>>is no reason to assume that it is anywhere nearly so important as the
>>computational complexity aspect of a machine as large as the brain.
>>
>>As a counter to your doctrinaire view, consider the following
>>anthropic hypothesis about why synapses are as huge as they are: in
>>the course of evolution, there were many variations that involved
>>making smaller, less reliable neural circuits that were more affected
>>by quantum, thermal, and chemical chaos.  Those variants were weeded
>>out by non-survival.  What remains is a very stable brain, equipped
>>with huge synapses, micron-diameter small fibers, and very effective
>>blood-brain barriers.  Yes, there have been brains afficted with
>>uncertainty, but evolution disposed of them as they deserved!

Taking the last first, why did brains "...afflicted with uncertainty"
deserve to perish?

It is probably true that each synaptic transmission is so macroscopic
that quantum effects have no significant impact. However, as Minsky
mentions, chaotic effects could play a role in the nerve cell behavior.
Each neuron produces an output in response to the inputs - excitatory and
inhibitory - that it receives. The thresholds for firing are surely variable
from cell to cell, and over time. I can well imagine that the precise
threshold is chaotically controlled over some range, so that a given cell
might fire at one time, and not at another, depending upon chemically
controlled parameters which behave chaotically within narrow ranges.

Does anyone here have any hard data to back up or refute these speculations?

Regards,
       H. Biesel




