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Downloading the Sensory Nuclei

Harry Erwin erwin at trwacs.fp.trw.com
Tue Nov 24 21:48:56 EST 1992


I've been going through Freeman and Yao's 1990 paper in detail. It's very
interesting, and I'll post some comments tomorrow. I want to post a note
right now, though, on how the cortex downloads the sensory nuclei. It's
rather interesting.

First, as Desimone demonstrated in September, neurons report not just
their conclusions, but also the evidence for those conclusions. This turns
out to be important. The Anterior Olfactory Nucleus (AON) is the component
of the olfactory system that receives the pattern from the Olfactory Bulb
(OB, also referred to as the Olfactory Nucleus). It can pull the OB to a
neural state by afferent synapses onto the granule cells. Simultaneously,
it can feed synthetic sensory data into the mitral cells (which the
sensory neurons synapse onto as well). Where does it get the correlation
between the sensory data and what the OB is reporting to it? The OB
reports not just patterns, but the evidence for those patterns. Hence the
AON can learn how to simulate any sensory input.

The AON feeds the cortex further downstream with pattern data. It is also
able to detect the neutral state and the novel object states. Since it
receives the sensory data associated with the novel object, it can feed it
back, simultanously  pull the OB to a neutral state, and so train the OB
to recognize the pattern. It correlates the pattern with the object it was
trying to train the OB on, using the retained sensory data. (Remember,
neurons are _good_ at learning patterns. Visual system neurons can retain
hundreds of individual features on one presentation each. This seems to
involve synaptic switching, rather than synaptic growth.) These patterns
don't need to be learned permanently--it's good enough to retain them for a
period of time and then discard them. Hence, the lack of invariance. The
AON can instead use synthetic sensory data to find out what the OB
currently reports for a given pattern of data.

Neat, huh?! The OB does not do the model update. Instead, it passes
through the data needed downstream to do those updates. It appears that
semantic data networks are the way our brains naturally organize
information. Logic is not "natural." Instead what is natural is
overlapping cognitive domains.

This is a little like what I do when I redirect processed sensory input
through a sensory processing area. This is also how higher cortical
functions might "envision" manipulating a scene or object--rotating it,
etc.

Cheers,

-- 
Harry Erwin
Internet: erwin at trwacs.fp.trw.com



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