X-Message-Number: 5178
From:  (John K Clark)
Newsgroups: sci.cryonics
Subject: Beyond 2000 and Mind Uploading
Date: 14 Nov 1995 03:38:54 GMT
Message-ID: <48930e$>

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First of all I want to thank Brian Wowk for answering my questions about MRI.

                >>John K Clark                    

                >>My suspicion ( and I admit it's only a suspicion) is that
                
                >>a 1 nanometer resolution would be far more than what you
                
                >>would need for uploading, a resolution of a hundred, perhaps
                                >>a thousand times less might be sufficient.

        >Brian Wowk            
        >I don't see how.  Neural anatomy (connection information) isn't       

        >enough. Don't you need *chemical* (i.e. molecular) information from
                >the synapses?

You could be right, on the other hand, it could turn out that
chemical information is involved in short term memory and in the
FORMATION of long term memory BUT that the memory itself is
encoded in the gross anatomy of the synapses. I don't claim that
this has been proven, but it is true that the  most important
storage mechanism is thought by most to be Long Term 
Potentiation ( LTP). It theorizes that memory is encoded by
varying the  strength of the 10^14 synapses that connect the
10^11 neurons in the human  brain. It had been thought that LTP
could be specified to a single synapse so  each synapse was
equivalent to one computer bit, perhaps several bits, but  now
it looks like that is a vast overstatement.

In the January 28 1994 issue of Science Dan Madison and Erin Schuman 
report that LTP spreads out ( the LTP signal is probably sent by 
the diffusion of nitric oxide) to a large number of synapses on 
many different neurons. The individual synapse cannot be the computer bit 
of the brain. Neural Net expert Terrence Sejnowski commented on these new 
findings " 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".

All this severely reduces the storage capacity of the brain but 
increases it's redundancy. This is good news if we want to
repair a badly damaged frozen brain. Also, although it may hurt
our pride to think that our essence can be defined with less
information than we thought, it also means that uploading will
be easier ; there's less you need to upload. 

It's not obvious to me that we must need an astronomical amount
of long term  memory in order to function. I've heard that some
medical specialists were  distressed to find that AI programs of
just a few megabytes could make pretty good diagnoses in their field. 
Considering the years it took them to acquire this knowledge, 
they expected that a much larger program would be needed.       


                                            John K Clark     


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