Anders Sandberg <nv91-asa@nada.kth.se> On The Extropian List on March 17 1997:
>Knowing the what the hardware looks like might help us deduce the
>internal properties, but this is likely to be highly nontrivial
>since it is hard enough to distinguish one cell from another using
>visible light.
That's because we usually only have a picture of a very thin cross section
of a cell, if you could see the entire cell in 3D things would be different,
even if the resolution was no greater that found in a good visible light
microscope. The new popular visible light confocal microscope certainly helps
with this depth of focus problem, I was surprised when I learned it was
invented by the versatile Marvin Minsky, better known as the father of
artificial intelligence, he not only thought up the idea he actually built
the first one.
>how do we tell apart the different chemical states that are
>important for brain structure and function (like what
>neurotransmittor a given synapse uses or what state of LTP it is in)
>using optical information?
I'll bet you could tell if a synapse had undergone LTP or not, you probably
could not tell how it was using neurotransmitters, but maybe we'd get lucky
and find there is a gross physical change.
On Cryonet thomasd@netcom.com (Thomas Donaldson) on Sun, 16 Mar 1997 Wrote:
>I suggested what is basically a nanotechnological method for readout.
Yes, that would be much better and I know that would work, but I was hoping
something could be found before we had Nanotechnology.
>a model or simulation is not the same as the thing itself, no matter
>how good it may be.
Is my copy of Windows NT not the same as the "original" at Microsoft
headquarters? If I have not convinced you that I am correct it's because the
post you're looking at is not as good as the "original" on my computer.
Joseph Strout <jstrout@ucsd.edu> on Mind Uploading List on March 17 1997:
>Visible light doesn't have the resolution needed; under ideal
>conditions in a microscope, the best you can do is about 200
>nanometers.
If you had 200 nanometer resolution in 3D you could certainly tell what
synapse went where, whether you could obtain enough other information about
it for an upload I'm not sure.
>This is an order of magnitude too poor.
If so then you'd need light with a wavelength of 40 nanometers, that's in the
Ultraviolet region not in the X ray, and I think that's an improvement.
Actually there is a way to resolve very small objects even with very large
waves.
More than 100 years ago Ernst Abbe "proved" that details smaller than half
the wavelength of the light used to illuminate a specimen could not be
resolved, but he made a hidden assumption, namely that the distance between
the specimen and the source of light was large compared to the wavelength.
In 1956 J.A. O'Keefe proposed a "scanning near field microscope" that would
break the Abbe barrier. O'Keefe said that if light was emitted from a tiny
hole less than a wavelength away from the specimen then the resolution would
be limited only by the size of the hole, the wavelength of the light would be
irrelevant. In 1972 Eric Ash proved experimentally that O'Keefe was correct.
It looks like this technique may be practical for some things. In 1993
Eric Betzig of ATT used visible light from a laser 10 nanometers above a
sample to reveal details of the skeletal scaffolding inside a cell as small
as 15 nanometers. Visible light is about 500 nm.
I don't know how you could use this technique for 3D brain scanning, that's
why I mentioned it, I need some help, put your thinking cap on people.
John K Clark johnkc@well.com
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