[ExI] meaning & symbols

[Eric Messick]

Ben writes:
>OK obviously this word 'symbol' needs some clear definition.
>
>I would use the word to mean any distinct pattern of neural activity
> that has a relationship with other such patterns.  In that sense,
> sensory symbols exist, as do (visual) word symbols, (auditory) word
> symbols, concept symbols, which are a higher-level abstraction from
> the above three types, and hundreds of other types of 'symbol',
> representing all the different patterns of neural activity that can
> be regarded as coherent units, like emotional states, memories,
> linguistic units (nouns, verbs, etc.), and their higher-level
> 'chunks' (birdness, the concept of fluidity, etc.), and so on.

This sounds exactly like what I mean when I use the term "symbol" in
this context.

The question came up about how hard it might be to tease apart
*distinct* patterns of neural activity.  I agree that this is likely
to be tricky.  I expect many symbols will be active in a brain at the
same time, and differentiating them could be hard.  They may change
representation with the brain region they are active in.  I do expect
that a symbol is simpler than a global neural firing pattern, though.

If a firing pattern in one part of the brain triggers a similar firing
pattern in another part of the brain, is the same symbol active in
both areas, or are there two distinct symbols?  I don't think we have
a good enough handle on this to answer such questions yet.

-eric