Semantics and Syntactic Representations

Leslie Kay lmk2 at garnet.berkeley.edu
Tue Nov 30 16:15:47 EST 1993


In article <2dftqe$d33 at truffula.fp.trw.com>,
Harry Erwin <erwin at trwacs.fp.trw.com> wrote:
.....
>in the ionic currents associated with K0 systems in the brain. At the same
>time, Walter J. Freeman has recently presented evidence that his KIII
>model of the olfactory system generalizes to all the sensory modalities.

Although we hope this is true, really he has shown that primary sensory
cortices: visual, auditory, and somatosensory, show post stimulus regions
where spatial patterns of activity measured at the surface of the cortex
can be discriminated as to which stimulus they are produced in response to.
In other words, the spatial patterns exhibited in the olfactory bulb also
occur in the other primary cortices and in the prepyriform cortex (primary
olfactory cortex).  They occur in response to a meaningful stimulus of
the same modality as the cortex.

>This KIII model is characterized by a lack of invariance--the point at
>which the initial semantic classification of a pattern as being of
>interest or not of interest is at the initial entry of the sensory stimuli
>into the brain. Simulation work has begun to clarify the nature of this
>processing. It seems to involve rapid pattern matching coupled with

it doesn't do pattern matching.

>conditioning (to set up patterns for future matching) and habituation (to
>ignore patterns in the input stimuli that are not of interest). The deeper
>cortices appear to control these processes through feedback (reafference),
>in a manner that appears to involve mechanisms that allow the deeper
>cortices to condition earlier cortices to detect specific patterns of
>sensory data (perhaps through pathways that allow the deeper cortices to
>generate 'synthetic sensory data'). Since these reafferent pathways appear
>to involve some sort of inverse morphism to that which translates the
>afferent sensory data as it is processed, this allows the deeper cortices
>to determine the semantically meaningful sensory patterns they are seeking
>and to prime the initial sensory processing to respond with semantically
>meaningful signals when those patterns are detected.

actually, this is still hypothetical and my work in progress, but I would
like to stress that this is probably not a "translation" and pattern
matching process.  These sensory processing areas can be seen as a
dynamical system where each part contributes to the whole system 
entering a state which is the perception, thus dispensing with the need
for pattern matching.

The rest is not Freeman's theory and is pertinent more to pattern 
matching systems than his theory.

Thanks,

Leslie Kay
lmk2 at garnet.berkeley.edu



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