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Right visual field to left hemisphere. Why?

kkollins at pop3.concentric.net kkollins at pop3.concentric.net
Mon Oct 12 20:18:25 EST 1998

Matt Jones wrote:

> In article <6vbui9$htg at dfw-ixnews10.ix.netcom.com> F. Frank LeFever,
> flefever at ix.netcom.com writes:
> > Maybe I've misread, or maybe, your being so heavily invested at the
> >molecular level (I checked out your two abstracts in upcoming Society
> >for Neuroscience program), you really have slipped up on a molar (gross
> >anatomy) level.  Both sensory and motor fibers are crossed, so
> >something appearing in the right visual field would go to left
> >hemisphere, yes, but most direct motor response from that hemisphere
> >would be to the muscles on the RIGHT side of the body, not the left.
> >
> Oops! Right you are. The hypothesis I suggested would only work if you
> went straight from the right eye to the muscles on the left side,
> bypassing any central motor neurons (are there any vertebrates organized
> like this?). Thanks for the correction and the additional comments.
> -Matt

  The tree shrew is wired up in the fairly-primitive way that's been
discussed. In most mammals, the neural-fiber crossings ("decussations")
occur for a reason that's a tad more-complex. The most-basic, and
relatively-licalized, problem is to avoid "stimulation" that causes tissue
damage, and decussation handles that mightily. At higher-levels (cognitive)
the problem is transformed into a global-integration problem. Not only the
visual system, but =all= systems are topologically (geometry with twists and
turns and area stretchings or shrinkings) alligned so that
neural-impulse-bourne information is always mapped so that it coincides
exquisitely with the lower-level prerequisite of avoiding "stimulation" that
damages body tissue. Consciousness is enabled in this way... every part of
the nervous system "comprehends" what's going on in every other part of the
nervous system because of this exquisite topological "hand-shaking". All of
this can be taken all the way down to the molecular level, and it all stands
proven (and has for more than a decade). ken

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