[ExI] Vermis ex machina

John Clark johnkclark at gmail.com
Tue Mar 3 15:26:18 UTC 2015

On Tue, Mar 3, 2015  Anders Sandberg <anders at aleph.se> wrote:

>> IMost think that Long Term Potentiation is the molecular basis of memory
> and in the January 28 1994 issue of Science Dan Madison and Erin Schuman
> found that Long Term Potentiation spreads out, by diffusion of Nitric Oxide
> (NO), over several cell diameters;  so you have lots of copies of the same
> identical information, so a single synapse can't be the equivalent of one
> bit of information, instead a bunch of potentiated synapses work together
> to store that one bit of information.
> > How well have that actually held up? There was a lot of interest in it
> back in the 90s, but I have not seen much mention of it over the past 15
> years. There are a few papers talking about lateral LTP like
> http://www.ncbi.nlm.nih.gov/pubmed/25260706 but most just talk about NO
> as relevant locally for LTP.

The Nitric Oxide would only diffuse over a few cell diameters but each
neuron has about 1000 synapses so that could include a lot of synapses. I'm
not sure if that would be called local or not.

> > you could have one bit per synapse on average but distributed across a
> few neighbours: their potentiation levels would contain a mixture of
> several bits, individually retrievable by the right stimulation pattern.

Maybe, but it seems to me that with a system like that you'd have the worst
of both worlds. You'd have inefficient and slow storage because before
making a new memory you'd have to make sure it didn't randomly change an
existing memory, but you'd have little or none of the sort of redundancy
that could be easily used for error correction. But of course just because
it's a crazy primitive design is no guarantee that Evolution didn't decide
to do things that way because evolutionary winners don't have to be the
best possible they just have to be better than the competition.

  John K Clark
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