From: hsr4@vax.ox.ac.uk (Auld Sprurklie)
Newsgroups: sci.nanotech
Subject: Re: Multiple Experiences
Date: 8 Sep 92 19:52:32 GMT


In article <Aug.29.01.49.26.1992.13201@planchet.rutgers.edu", mckendre@sal-sun70.usc.edu (Thomas Mc Kendree) writes:
" In article <Aug.21.18.26.44.1992.20235@planchet.rutgers.edu" hsr4@vax.oxford.ac.uk (Auld Sprurklie) writes:
""Making a great many assumptions...
""What was NMR and is now MRI (Magnetic Resonance Imaging) is a mechanism for
""monitoring the chemical state of part of an organism (this necessarily very
""vague).  If the speed of MRI can be increased considerably to the point where
""it can take a 'snapshot' of the chemical state of an entire brain, frozen in
""action for a moment, and then process that chemical map to yield whatever
""format would be necessary for an artificial brain, and then implement that new
""map in the artificial unit....
" 
" I believe that it might be necessary to take many 'snapshots' and actually
" make a movie, before you really understood how a brain was structured.
" 
" From the standpoint of using MRI, however, there may be a much more important
" problem; I believe that the nature of MRI makes it impossible to get resolution
" down to the individual neuron, because of the fundamental resolution of the 
" magnetic "rays."  Even if that can be addressed (perhaps the wavelength can
" be reached, and one could have a giant battery of phased array SQUIBS, or some
" such), the way MRI works, it measures brain activity by looking at the 
" distribution of an atomically tagged chemical (e.g. inject sugar with a special
" isotope.  The cells that are "running hard" at the time draw in the sugar, and
" by using the MRI to look at the distribution of the isotope, infer the 
" distribution of how neurons drew upon the sugar.)  
" The upshot is that every neuron might not have the tagged isotope for any
" MRI scan to pick up, and even if they all do, there still is no obvious way
" to read out all the synapses.  I would be very interested if anyone can show
" a non-invasive technique for reading off all the structure, and hence contents,
" of the brain.  (Reading EOC gives one an idea of how this could be done
" non-destructively, albeit invasively.)

Apologies for the delay in responding to this - brief break away from it all :-)

Unless MRI has changed over the last few years, no isotope tagging is necessary-
that's one of it's beauties.  The last time I had contact with the technique,
the system was tuned to a particular element after having been standardised on
for example Hydrogen in, say, water (one might tune it to phosphorus, for 
example) and then a series of scans are made, the mean being representative of
the phosphorus activity over a period of time.  A faster system would scan in
real time, and might scan for more than one element.  A researcher some years 
ago who pioneered the use of NMR (as it was known then) said to me that it was
readily possible for single cell activities to be monitored.

Since this has been a very speculative thread, I had carried the speculation
further afield to try and encompass technologies which are already targeted
at the single cell level.  I don't think I went too far out on a limb... 
" 
" [I wouldn't want to upload via such a (MRI) technique--much too vague,
"  and too much chance of completely missing latent memories one isn't
"  thinking about at the time.  But by the same token, it might be a way
"  to generate "partials".
"  --JoSH]

MRI was (as I understand it) originally conceived as one of a series of steps
leading ultimately to a non-invasive surgical system capable of diagnosis and
treatment at the single cell level.  I don't think it was envisaged as a route
for brain-cloning, more as a mechanism for diagnosis of cell abnormality in, 
say, the kidney, to be then followed by fairly simple surgery in the same vein
(oops) as modern focussed radiotherapy (i.e., targeted at one or a few cells).

One possibility, I thought, was to engage a subject in a particular skill which
had already been learned, scan the subject's brain for cellular activity (which
should then highlight which neurons are active during the exercise) and then
clone those cells.  I think it might work, but I am doubtful (still trying to
find a way which I feel will lead to a practical method of cloning).

The beauty of MRI is that it is potentially capable of providing a snapshot of
the exact chemical state of a group of cells at a given moment, for a series of
such moments.  Whether that's useful, of course, depends upon the exact nature
of skills as they appear in biological neural network terms.

Peter "Who is Emma Rye anyway ?" Brooks