On Wed, 8 Jan 1997 Eugene Leitl <Eugene.Leitl@lrz.uni-muenchen.de> Wrote:
>But NO is not the only neurotransmitter/neuromodulator,
>there are several (some say several 100) kinds of neuron
>classes, and many kinds of synapse types, oodles of different
>neurotransmitters.
All true, but it doesn't change the fact that LTP refuses to stay put in
a single synapse but spreads out, so if LPT is part of long term memory then
the maximum storage capacity of the brain just went south.
>NO's diffusion range is also certainly limited. Does it
>really affect hundreds of synapses?
I don't think anybody knows how many synapses it changes, I said 1000 but that
was just a guess. I do know that the concentration of synapses is very high
in the brain, so the radius of a sphere that contained 1000 synapses would be
pretty small, the NO would not have to defuse very far before it started to
reset a lot of synapses.
>Sejnowski is certainly very well known. But this doesn't
>mean NO diffusion-induced potentiation is the silver bullet,
>to explain away every single mystery.
Nobody said it did, but it does drastically revise downward the amount of
information the most popular information storage mechanism in the brain can
handle.
>>Sejnowski:
>>"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".
>Eugene:
>That would be very good news, if true.
Yes indeed, not only does it mean that there is less information to upload but
the massive redundancy means there is a better chance of extracting the needed
information from even a badly damaged frozen brain.
>>John:
>>The chance that Evolution would just stumble across
>> the simplest solution is astronomically small.
>Eugene:
>Yes, but generating _many_ subsystems when a single one would
>have been sufficient... The evolutionary distance should be,
>at least intuitionally, larger.
Evolution can't backtrack, it has no foresight so every mutation must benefit
an animal NOW or it won't survive. Once biology sets a standard it would be
hell to change it, think of the trouble we have in changing to a new computer
operating system, even if the new one is a lot better, then multiply that
difficulty by about a billion.
>Hauling heavy noble gas atoms on a cold Ni surface/reversibly
>poking holes in molybdenum disulfide surface is one thing,
>writing diamondoid billion-atom-carbon-structures from active
>species is another matter entirely.
Agreed, massive engineering questions remain, but that's what they are,
engineering. Carbon atoms, Nobel gas atoms, a kids paper airplane and a
thousand ton cargo jet, all obey the same laws of physics.
>That a wrong comparison. Mechanosynthesis didn't have its
>Wright bros. yet.
In 1687 when Isaac Newton wrote the most important book in the history of the
world, he would have had to say that a rocket to the moon did not violate any
known physical law.
>>John:
>>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.
>Eugene:
>Yes, but can it generate/break is specifically
I don't know but it seems like a pretty good bet to me, different atoms
resonate at different frequencies.
>doubtlessly STM can do atomic manipulation. Question is: is
>the capability sufficient for autoreplication/all purpose
>mechanosynthesis?
I could be wrong but I very much doubt that a STM could do that, but it might
be able to make something that could, or make something that makes something
that could. At ant rate, it certainly proves that it's possible to manipulate
individual atoms, the rest is just engineering, although I admit an awful lot
of engineering.
John K Clark johnkc@well.com
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