On Mon, 6 Jan 1997 Eugene Leitl <Eugene.Leitl@lrz.uni-muenchen.de> Wrote:
>While my estimate may be too high yours is certainly
>drastically too low.
Unless Long Term Potentiation turns out NOT to be an important part of
Long Term memory, and that doesn't seem very likely to me, my estimate of
.001 bit/synapse must be closer to the truth than yours of 50 bit/synapse.
The Article I referred to in the January 28 1994 Science is by Dan Madison and
Erin Schuman, I would not be surprised if it earns them a Nobel Prize someday.
They found that when a synapse strengthens it's functional link to another
neuron that synapse releases a chemical (nitric oxide) that diffuses to many
other synapses and causes those synapses to be strengthened also. If, as most
think, long term memory is encoded by varying the strength of the 10^14
synapses that connect the 10^11 neurons then the conclusion is obvious.
Apparently I'm not the only one who thinks so. Terrance Sejnowski of the Salk
institute, one of the best neural modeler's in the world, certainly believes
that this reduces the storage capacity of the brain. In an editorial in the
same issue of Science that Madison and Schuman announced their results he
says "The individual synapse cannot be the computer bit of the brain. Instead
of thinking of a synapse as representing a piece of information, you can now
begin thinking of a population of potentiated synapses acting together".
>Evolution doesn't produce complex circuitry for no good
>reason, if a simpler one would have been sufficient
I profoundly disagree. The chance that Evolution would just stumble across
the simplest solution is astronomically small. The winner in the battle of
Evolution is not the one who has the perfect solution, just the one that
finds a solution that is better than the competition. Evolution is slow and
stupid, but I seem to remember you and I going down this road before.
>What is the purpose of a discrete, modular, pretty precise
>structure if all it is good for is storing just .001 bits.
There is no purpose, Evolution just screwed up. You're not the first to be
disappointed by Natures ineptitude as seen in these new findings. Roger Nicoll,
a neuroscientist at the University Of California was yet another scientists
quoted in the same issue, he was rather blunt: "Very Provocative. Nature has
gone to elaborate lengths to create a structural edifice that can give you
synapse specificity. To then just degrade the process and let it spread
around a bit, makes it seem like Nature blew it somehow".
>Ask Joe Strout, he burns any number of MFlops for hours to
>simulate just _one_ biologically realistic neuron, and far
>from running in realtime.
The complexity of an individual neuron is irrelevant, the Madison and Schuman
findings are about redundancy. The point is, it may not take any more computer
power to simulate many neurons than to simulate one.
>We don't know whether it [Nanotechnology] violates the laws
>of physics. It may, it may not.
Nanotechnology is just the ability to move atoms with tolerances that are
very small by everyday standards but still larger than the minimum tolerance
allowed by Heisenberg. We've already moved atoms around with a STM, so what
Law of Physics could Drexler's Nanotechnology be violating? I think it must
be the same one a 1000 ton airplane would be violating.
>>John:
>>It's your responsibility to prove it's impossible
>>not mine to prove it's possible.
>Eugene:
>Wrong. Science works differently. _You_ have to prove it,
>not vice versa.
Yes, if you say a perpetual motion machine or The Lorrey drive is impossible
it's your responsibility to prove they are impossible, and you can quite
easily do so by pointing out that one violates the law of conservation of
energy and the other violates the law of conservation of momentum. If you say
that a 1000 ton airplane is impossible you have to prove that there is a new
law of Physics that places an absolute limit on the weight of flying machines.
I don't think you can do that.
>No man-made mechanosynthesis works. A STM demonstration of
>basic set of mechanosynthesis reactions, validating computer
>runs is sufficient for _me_. We don't have such evidence
It's true we can't make molecules to order with a Scanning Tunneling
Microscope (STM), or if we can we can't find them yet, detecting the product
of such a reaction is probably more difficult than causing it. However there
is no reason to think a STM can only do Physics and not Chemistry, if it
turned out to be true that would prove the existence of some mysterious new
physics we know nothing about. It would have to be mysterious indeed because
we already know a STM can break a chemical bond.
In the June 16 1995 issue of Science it's shown that if electrons of the
correct energy are shot at an atom from the tip of a STM the atom will
resonate and the resulting vibration will break the chemical bond. According
to the researchers the procedure is somewhat faster than they expected and
it does not require any exotic conditions such as very low temperature.
J.W.Lyding, one of the authors of this report, is quoted as saying " We'd
like to make small, electronic devices on the nanometer scale".
Also, as you know Carbon tubes of nanometer diameter are pretty easy to make,
recently it's been found that molten vanadium oxide can form a coating on
these carbon tubes, the carbon can then be dissolved away using conventional
chemical techniques leaving pure vanadium oxide tubes of nanometer diameter.
Vanadium oxide is a powerful catalyst for many chemical reactions, so it
should be possible to use them as tiny test tubes, Chemistry done very small.
You could also use them as molds for all sorts of different materials.
John K Clark johnkc@well.com
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