> -----BEGIN PGP SIGNED MESSAGE-----
>=20
> On Mon, 6 Jan 1997 Eugene Leitl <Eugene.Leitl@lrz.uni-muenchen.de> Wrote=
:
> =20
> >While my estimate may be too high yours is certainly=20
> >drastically too low.=20
>=20
> Unless Long Term Potentiation turns out NOT to be an important part of=20
> Long Term memory, and that doesn't seem very likely to me, my estimate of=
=20
> .001 bit/synapse must be closer to the truth than yours of 50 bit/synapse=
.=20
Most of these 50 bits is connected-to-neuron-ID, one needs a lot of bits=20
to absolute-address 10^11 neurons. The delay might not be necessary for an=
=20
AI, yet it is certainly relevant for a realistic upload, so a few bits=20
should be reserved for the delay representation, either. The type of the=20
synapse, the strength, etc. Did I say 50 bits? Make that 64.
=20
> The Article I referred to in the January 28 1994 Science is by Dan Madiso=
n and
> Erin Schuman, I would not be surprised if it earns them a Nobel Prize som=
eday.
Thanks for the valuable pointer. Have been neglecting Nature much=20
too much lately.
> They found that when a synapse strengthens it's functional link to anothe=
r
> neuron that synapse releases a chemical (nitric oxide) that diffuses to m=
any
> 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.
But NO is not the only neurotransmitter/neuromodulator, there are=20
several (some say several 100) kinds of neuron classes, and many kinds=20
of synapse types, oodles of different neurotransmitters. NO's diffusion=20
range is also certainly limited. Does it really affect hundreds of=20
synapses?`
=20
> Apparently I'm not the only one who thinks so. Terrance Sejnowski of the =
Salk=20
> institute, one of the best neural modeler's in the world, certainly belie=
ves
Sejnowski is certainly very well known. But this doesn't mean NO=20
diffusion-induced potentiation is the silver bullet, to explain away=20
every single mystery.
> that this reduces the storage capacity of the brain. In an editorial in t=
he
> same issue of Science that Madison and Schuman announced their results he
> says "The individual synapse cannot be the computer bit of the brain. Ins=
tead
> of thinking of a synapse as representing a piece of information, you can =
now
> begin thinking of a population of potentiated synapses acting together".
That would be very good news, if true. Otoh, it would require translation=
=20
of the scanned biological circuitry in some other coding, with a more=20
suitable mapping to the underlying hardware. It _is_ a straightforward=20
thought, yet it makes matters much more complicated. A yet another=20
nontrivial pass applied onto the data set...
=20
> >Evolution doesn't produce complex circuitry for no good=
=20
> >reason, if a simpler one would have been sufficient=20
> =20
> I profoundly disagree. The chance that Evolution would just stumble acros=
s
> the simplest solution is astronomically small. The winner in the battle o=
f
Yes, but generating _many_ subsystems when a single one would have been=20
sufficient... The evolutionary distance should be, at least intuitionally,=
=20
larger.
> 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 a=
nd
> stupid, but I seem to remember you and I going down this road before.
=B4
Yeah, right ;) However, if evolution does indeed occur at such a grand=20
scale as biology, cosmogony, and coginitive science (Edelman's Darwin=20
mind), and even now GAs can produce super-human-level quality digital=20
designs, it might be not that slow (in its digital incarnation) nor that=20
stupid?
=20
> >What is the purpose of a discrete, modular, pretty preci=
se=20
> >structure if all it is good for is storing just .001 bit=
s.=20
> =20
> There is no purpose, Evolution just screwed up. You're not the first to b=
e
Evolution has no defined purpose, yet it artefacts a consistant higher=20
complexity trend, a longer taxa longevity, a higher cerebralization=20
coefficient, etc. After all, the step from archaebacteria to us meek mehums=
=20
is somewhat large, isn't it? The random-walk-back-to-the-wall argument may=
=20
seem plausible at first, howeve I don't think that's all. There is surely=
=20
some fiendish subtlety we haven't seen yet.
> disappointed by Natures ineptitude as seen in these new findings. Roger N=
icoll,
> a neuroscientist at the University Of California was yet another scientis=
ts
> 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 yo=
u
> synapse specificity. To then just degrade the process and let it spread
> around a bit, makes it seem like Nature blew it somehow".
It may be diffusion defines neighbourhood relation for conformal maps=20
(sombrero function), maybe it's for something utterly different. I know=20
that additional synapses sprout when the dynamic range of a single one is=
=20
exceeded, and they also mature, but diluting this complex machinery? I=20
dunno.
=20
> >Ask Joe Strout, he burns any number of MFlops for hours =
to=20
> >simulate just _one_ biologically realistic neuron, and f=
ar=20
> >from running in realtime.
> =20
> The complexity of an individual neuron is irrelevant, the Madison and Sch=
uman
> findings are about redundancy. The point is, it may not take any more com=
puter
> power to simulate many neurons than to simulate one.
Well, he doesn't do single units alone, he does (small) nets also.
=20
> >We don't know whether it [Nanotechnology] violates the l=
aws=20
> >of physics. It may, it may not.
> =20
> Nanotechnology is just the ability to move atoms with tolerances that are
"Move" is not move. Hauling heavy noble gas atoms on a cold Ni surface/reve=
rsibly=20
poking holes in molybdenum disulfide surface is one thing, writing=20
diamondoid billion-atom-carbon-structures from active species is another=20
matter entirely.
> very small by everyday standards but still larger than the minimum tolera=
nce
> allowed by Heisenberg. We've already moved atoms around with a STM, so wh=
at=20
Oh jeez, I was referring to the advertised positional mechanosynthesis tip=
=20
accuracy of 100 pm, which is an intrinsical property of the assembler arm=
=20
stiffness. I'd rather have 10 pm, since I regard 100 pm precision much=20
too coarse to generate almost-perfect-diamondoid lattice. Apart from that,=
=20
it's reversibility, a minimum reaction set (which set is minimal?), etc.
> Law of Physics could Drexler's Nanotechnology be violating? I think it mu=
st=20
> be the same one a 1000 ton airplane would be violating.
The stuff sure scales differently at these scales.
=20
> >>John:
> >>It's your responsibility to prove it's imposs=
ible=20
> >>not mine to prove it's possible.
>=20
> >Eugene:
> >Wrong. Science works differently. _You_ have to prove it=
,=20
> >not vice versa.=20
>=20
> Yes, if you say a perpetual motion machine or The Lorrey drive is impossi=
ble=20
> it's your responsibility to prove they are impossible, and you can quite
No, basicaly if they violate a very basic tenet of science you can just=20
lean back and let the proponents produce the evidence. The more=20
outrageous the claim, the more solid the evidence.
> 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 mach=
ines.
> I don't think you can do that.
That a wrong comparison. Mechanosynthesis didn't have its Wright bros.=20
yet.
=20
> >No man-made mechanosynthesis works. A STM demonstration =
of=20
> >basic set of mechanosynthesis reactions, validating comp=
uter=20
> >runs is sufficient for _me_. We don't have such evidence
> =20
> It's true we can't make molecules to order with a Scanning Tunneling=20
> Microscope (STM), or if we can we can't find them yet, detecting the prod=
uct
> of such a reaction is probably more difficult than causing it. However th=
ere
I doubt it, since STM has atomic resolution, and we already know where we=
=20
caused the reaction (e.g. hole in the surface). Finding the point of=20
interest should not be a problem. Caused a defined process on an atomic=20
scale, merely by bobbing the tip, and applying the voltage pulse is much=20
harder. I've watched an STM experiment which plucked Au clusters from the=
=20
gold tip, it wasn't trivial, and the clusters were not well defined.
> is no reason to think a STM can only do Physics and not Chemistry, if it
The distinction between chemistry and physics is highly arbitrary.=20
Quantum chemistry is pure physics, e.g. Mechanosynthesis is basicaly=20
physics/computational chemistry, pretty obscure disciplines, but that's=20
not a reason to my objections. Lack of evidecence/simulation validization=
=20
is.
> turned out to be true that would prove the existence of some mysterious n=
ew
> physics we know nothing about. It would have to be mysterious indeed beca=
use
> we already know a STM can break a chemical bond.
Yes, but can it generate/break is specifically, allowing us a minimal,=20
yet all-purpose mechanosynthesis reaction set?
=20
> In the June 16 1995 issue of Science it's shown that if electrons of the=
=20
> correct energy are shot at an atom from the tip of a STM the atom will=20
> resonate and the resulting vibration will break the chemical bond. Accor=
ding
So far, nothing outrageous.
> to the researchers the procedure is somewhat faster than they expected an=
d
> 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". =20
I doubt this means mass-production. The whole idea of nanotechnology is=20
that it can autoreplicate. Limited manipulation capability is almost=20
worthless, if we have to do it with macroscopic nonautonomous devices.=20
Perhaps I should elaborate: doubtlessly STM can do atomic manipulation.=20
Question is: is the capability sufficient for autoreplication/all purpose=
=20
mechanosynthesis? Nobody knows.
=20
> Also, as you know Carbon tubes of nanometer diameter are pretty easy to m=
ake,
> recently it's been found that molten vanadium oxide can form a coating on=
=20
> these carbon tubes, the carbon can then be dissolved away using conventio=
nal=20
> chemical techniques leaving pure vanadium oxide tubes of nanometer diamet=
er.=20
> Vanadium oxide is a powerful catalyst for many chemical reactions, so it=
=20
> should be possible to use them as tiny test tubes, Chemistry done very sm=
all.
Yes. The Heckl group now considers mounting nanotubes (not bucky) on tip=20
of the STM needle, possibly using photochemistry to activate precursors,=20
etc. But it's still not simple.
> You could also use them as molds for all sorts of different materials.
Interesting tech, certainly.
ciao,
'gene
=20
>=20
> John K Clark johnkc@well.=
com