On Fri, 28 Apr 2000, Michael LaTorra wrote:
> Previously in this thread:
> > I had written about the limits on cryonic storage imposed by
> > natural endoradiation and the issues involving information loss
> > by freezing damage.
>
> Mike:
> Thanks, Robert. I had not considered the fact that unstable isotopes within
> the frozen body would slowly damage surrounding cells. Is carbon-14 believed
> to be the main culprit?
K40 provides slightly more radiation (4400 Bequerels) than C14 (4080
Bequerels), but is uniformly distributed at low concentrations in the
cells (as K+ ions). C14 on the other hand is in and around the DNA
and has a much more damaging effect when it decays.
> Regarding loss of positional information, you indicate that ice damage
> should not be an insurrmountable problem because of the small size of
> synaptic and cellular structures which should match up uniquely. But are
> these truly unique? Or are there merely very many permutations?
My feeling is that they are unique within the possible physical dislocations
that could be caused by ice crystals. Nanobots will be able to trace
axon paths and detect synaptic clefts. Finding the matching surfaces
for a fracture across axon or syaptic cleft should not be difficult.
You have to consider that antibodies uniquely identify fragments of
9-12 amino acids (<< thousand atoms). Synaptic clefts containing
millions of atoms randomly distributed over axon terminals have to
present unique "images" whose mirrors can be recognized. In fact
because the genome cannot contain enough information to specify the
complete wiring of the brain and because the wiring of the brain
is feedback loop dependent on relatively unprecise molecular
diffusion and neuronal firing patterns, it is probably impossible
to get neuron connection networks that look very much alike at the
atomic level. At the higher level (e.g. motor neuron wiring) there
probably are patterns with small individual variations. That bodes
well for cryonics since even if the pattern is disrupted entirely,
an system with enough information should be able to re-wire you
a set of working motor functions. The real crux of the matter
is how distributed and redundant "you" are throughout your brain,
which will determine the degree to which local rewiring failures
that are not "general" can be tolerated.
But, IMO, I'd be much more concerned with whether the singularity
will have made reanimation of pre-S cryonics patients "irrelevant"
than I would with whether or not the technology will be up to the task.
> Perhaps like snowflakes, there are huge numbers of different
> configurations, but there is still some duplication because of
> the still larger number of instances.
Since the initial wiring occurs by randomly diffusing molecular
"attractants" and not by hard coded positional information, I
suspect there is a lot of variation. I believe that Finch and
Kirkwood have proposed that much of the variation one sees in
longevity is due to differnces in stochastic developmental processes.
If true, that would argue there is a lot of inter-individual and
local structural variation in brain structures as well.
Robert
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