What the Neocortex Does

Harry Erwin herwin at gmu.edu
Sun Aug 6 06:42:09 EST 2000

sisial <sisial at email.msn.com> wrote:

> First, I apologize for sending this response by e-mail.  I hit the wrong
> button.  I generally try to avoid e-mail without invitation.
> *************************************
> "Harry Erwin" <herwin at gmu.edu> wrote:
> >>> You're missing my point. Symbols are signs. They belong to a countable
> >>> set. Wind-tunnel models can vary continuously (or discontinuously). That
> >>> matters--there are some applications (for example in hydraulic analysis)
> >>> where symbolic modeling encounters an intractable problem, but analog
> >>> modeling works fine.
> >> Keeping in mind that I am still very new to all this, I am not sure I
> >> understand the distinction you are trying to make between "symbolic
> > > modeling" and "analog modeling".  Isn't the comparison of "symbolic" to
> >> "analog" something along the line of a comparison of metrics to
> >> precision?
> > Perhaps I would be clearer if I used the term 'formal model' rather than
> > 'symbolic model'.
> Not really; but please keep in mind my limited knowledge of the subject.
> "Formal model" to me seems pretty much synonymous with "symbolic model".
> The distinction between this and "analog modeling" still confuses me.  I
> mean, wouldn't an "analog model" simply be a "formal model" in which
> symbols, functions, and so forth are allowed to take on real values?

Formal model is basically anything that can be mapped to/from a Turing
machine. They are characterized by the use of symbol strings from a
finite alphabet. 

> There are formal models for analog recursive neural nets (ARNN).  Hava T.
> Siegelmann offers a really good overview of this area of research.

I'll nose into it.

Harry Erwin, PhD, <mailto:herwin at gmu.edu>,Computational Neuroscientist 
(modeling bat behavior), Senior SW Analyst and Security Engineer, and 
Adjunct Professor of Computer Science, GMU. Looking--CV available at: 

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