From: Ben Goertzel (ben@goertzel.org)
Date: Mon Jan 31 2005 - 06:30:29 MST
Hi,
> > True, but the brain is known to be highly
> > inefficient in many many areas,
> > e.g. (to choose a simple example) motion-direction
> > detection neurons that
> > are off by 80 degrees on average but are correct en
> > masse due to averaging
>
> This is not necessarily inefficiency. It may actually
> be very efficient. Neurons aren't "off by 80 degrees"
> so much as they have wide response zones and respond
> somewhat probabilistically within those zones.
> Neurons use redundancy to tolerate noise. In
> exchange, they can use much, much lower voltage levels
> (by about 5 orders of magnitude) than integrated
> circuits do, because they don't need to be completely
> reliable. This may lead to lower overall power
> requirements for a computation. You could work out
> the numbers for known systems, but it wouldn't be
> easy.
>
> There are also generally-accepted results showing
> that noise in neural systems is beneficial, but I
> don't really understand those papers, so I'll just
> say that not all "noise" in the brain is bad.
OK, well since we don't fully understand the brain (or anywhere near),
there's no way to conclusively settle an argument like this.
My best guess (based on reading a lot of neuroscience) is that viewed from a
computational perspective, the human brain has some wild inefficiencies in
it, but let's leave it at that.
> I think that whenever a "symbol" is active somewhere
> in anterior cortex, it is linked to, and activates (or
> is activated by), a series of cortical areas
> connecting it all the way back to the posterior
> sensory cortex. There's some evidence for this;
> primarily I'm thinking of experiments that show
> that visualization activates primary visual cortex.
Just because visualization activates primary visual cortex, doesn't really
imply or suggest that, say, abstract mathematical thinking does...
> Say you're using neural darwinism in cortex area A to
> select between different planned movement sequences.
> If you buy into my notion of how the brain works,
> that means that each competing program in area A has
> to be activating all of the other cortical areas
> that create/correlate with the "symbols" being used
> in area A. All the way back into sensory cortex,
> or at least premotor cortex. And to prevent
> collisions, that means that EVERY SINGLE CONCEPT
> stored in every cortical area needs to be stored
> hundreds of times over, so that these hundreds of
> copies can be activated separately and used
> simultaneously by competing programs in your planning
> cortex.
Yes, I see that Neural Darwinism contradicts your own speculative brain
theory ;-) ... Ok, that's fine... but that's different from saying it
contradicts known facts about the brain!
ben g
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