George Levy wrote:
[quoting Stathis]
>>You would also need to 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.
>
>
>This is unfair. According to this strict standard you are not the same
>person today as you were yersterday. In fact even an automotive
>transportation method would violate the above standard. We can't expect a
>Star-Trek tranporter to have more "High Fidelity" than a car. The question
>is how much can we relax the standard until the person at the output is
>"not the same" as the person at the input. In a brain substitution
>experiment, when should the patient say "yes doctor" or "no doctor"?
The "high standard" I have described does not go nearly as far as copying
the exact quantum state of every atom. It is merely aknowledging the fact
that information in brains is not stored in the anatomical arrangement of
neurons, any more than data on a computer is stored in the computer's
circuit diagram. If you copy a car down to the scale of a fraction of a
millimetrel you can expect that the copy will work the same as the original,
but if you copy a computer down to the sub-micron level you might end up
with a machine that will run Windows XP or whatever, but you won't copy the
data in RAM or on the hard drive. While it is not known exactly how
information is stored in a brain, it is certainly dependent on such
parameters as ionic gradients across cell membranes and the type, number,
distribution and conformation of receptor and ion channel proteins. At its
simplest, the brain could be seen as using a binary code, each neuron having
two possible states, "on" or "off". However, a snapshot of the state of each
neuron will not allow a model of the brain to be built, because all the
anciliary cellular machinery as above is needed to work out how to get from
one state to the next. If it were otherwise, why would all this complexity
have evolved?
--Stathis Ppapaioannou
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Received on Wed Jul 06 2005 - 22:53:12 PDT