From: Martin Striz (metastriz@yahoo.com)
Date: Tue Feb 01 2005 - 18:39:49 MST
--- "Eliezer S. Yudkowsky" <sentience@pobox.com> wrote:
> Phil Goetz wrote:
> > The problem is harder than is suggested by the 200Hz
> > figure. That is a spike-firing frequency.
> > In many cases, we believe info is encoded in the
> > firing rate,
>
> I have previously disputed this assumption, not least because of its
> consequence. (Ten steps is just ridiculous...) Neurologists can easily
> count spikes. Decoding information is much harder. Thus, I suspect that
> many complex encodings are reported in journals as "firing rates" because
> that's what neurologists know how to measure and they don't know what's
> being computed, let alone how to decode it.
Here's another plausible mechanism: some neurons act as stimulus intensity
gates, responding to a stimulus only when it produces a large enough number of
spikes from a single neuron. That's one way to filter out noise. I should say,
though, that the analogy of computation probably only holds for synapses acting
as logic gates. What occurs within the dendrites amounts to conformational
changes in proteins as a response to vacillations in environmental conditions
(in this case, the dielectric constant of water). That's why you need two
neurons to do the job: the one firing rapidly and the other setting the
threshold. That's your computation.
Martin
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