On Wed, Jul 06, 2005 at 10:31:50PM +1000, Stathis Papaioannou wrote:

> This may be getting a little off topic for this list, but it has always 
> seemed to me hopelessly naive to think that a person's mind could be 

Perhaps, perhaps not. 

> emulated from cryopreserved brain tissue. It would be like trying to 
> recreate a telephone conversation by examining a diagram of a city's 
> telephone network. Even if you could get the anatomy correct, which would 

This is not a correct analogy. Individual spike trains are readily
regenerated from a neuron circuit. Neurons are not people on the telephone.
There's nobody using your telephone network above but whatever intrinsic
activity there is in the network itself.

> mean knowing every neuron's connection with every other neuron, you would 

Of course. Empirically, submolecular resolution is available (cryo AFM).
Whether it is going to be needed (say, to read the degree of phosphorylation
of a protein, or identify individual ion channel type) is another question.

The information is there, and we can almost access it with current 
technology (completely ignoring scaling up issues).

> have nowhere near enough information to model a human brain, let alone a 
> particular human brain state at the time of death. You would also need to 

Which information you think would be missing?

> know the electrical potential at every point of every cell membrane; the 
> ionic gradients (Na, K, Ca, pH and others) across every cell membrane, 
> including intracellular membranes; the type, position and conformation of 
> every receptor, ion channel and other proteins; the intracellular and local 
> extracellular concentrations of every neurotransmitter; the workings of the 
> cellular transport, synthetic and repair mechanisms for each neuron and 
> probably also for each supporting glial cell; the intracellular and 
> extracellular concentration of other small molecules such as glucose, O2, 
> CO2; how all of this is changing with respect to time; and probably 
> thousands of other paramemters, many of which would currently be unknown. 

We empirically know that individual animal or human pattern can resume from zero
electrochemical activity and about zero metabolic activity (few degrees above 0 
We also have evidence (not fully validated yet) that vitrified retransplanted 
(renal, so far) tissue is viable.

Taken together it strongly hints that there is enough information, and that
most of above factors cited are empirically incorrect. You don't need them.

There might be showstoppers yet, but current trends are good. Some publications
are in the pipeline, hang on for a year or two.

> Most of this information would probably be lost post-mortem, but even if 
> some process could be found that preserves it, the sort of technology 
> needed to scan a brain at this sort of detail would probably not be far 
> short of atom for atom matter duplication and teleportation.

You cannot scan a living cephalon without invading it with several liters of
active nanomachinery. Most likely, no such machinery will be available within
our lifetime.

Because of this I'm focusing on cryopreserved people.

Eugen* Leitl <a href="http://leitl.org";>leitl</a>
ICBM: 48.07100, 11.36820            http://www.leitl.org
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