IUBio

Cross - Wired Eyes

George Hammond ghammond at mediaone.net
Tue May 15 21:41:42 EST 2001


maxwell wrote:
> 
> Richard Norman <rsnorman at mediaone.net> wrote in message news:BD9M6.57289$yd.357661 at typhoon.mw.mediaone.net...
> > "George Hammond" <ghammond at mediaone.net> wrote in message
> > news:3B00D9EE.9B6CC68A at mediaone.net...
> > > maxwell wrote:
> > > snip
> > >
> > > > Well, yes, I did as much. I'll note that your earlier
> > > > mention of the probable phylogenic constraints,
> > > > that resulted in decussations, consistent with current
> > > > ontogenic molecular findings, are another
> > > > pleasant spot of actual science amidst the folderol.
> > > > ...Which apparently evoked no further interest, alas.
> > >
> > > [Hammond]
> > > Is it plausible that decussation originated in
> > > the fact that a lens "reverses" it's image, and the
> > > easiest way to correct this unwanted optical circumstance
> > > would be to simply "reverse" the wiring somewhere else
> > > in the system.  To wit: do animals without eye lenses normally
> > > exhibit a major decussation in the CNS, or is this
> > > reserved only for animals with lenses?
> >
> > Maybe it sounds plausible, but unfortunately there is no
> > validity to it.  Nothing in the nervous "cares" whether the
> > image is inverted or reversed or upside down or whatever.
> > The mapping of the visual field to the cortex is highly
> > distorted over a highly folded surface.  Still we see "up"
> > and "down".  Besides, the auditory system and the
> > somatosensory systems, not to mention the motor
> > systems, are also decussated.
> 
> I can add nothing to the excellent reply you've posted save
> to note that even functional perception is not constrained
> by retinotopic representation-- subjects have worn inversion
> prism glasses, and after many days or perhaps weeks of
> the disorienting perception of an upside-down world,
> they adapt, and come not to show decrements in motion
> --unless they remove the prisms, but this change-over
> acquires greater 'ease-of-transition,' with repetition, and comes
> to switch rapidly in respect to demand state, though long-term
> optical rearrangements have perseverant aspects.

[Hammond]
Obviously another incompetent answer.  People can learn to
write with their feet, that doesn't mean it's not an impairment.
obviously the act of natural selection which decussated the CNS
was a godsend for animals who had recently developed lenses.
Poor scholarship on your part I'm afraid.
-- 
BE SURE TO VISIT MY WEBSITE, BELOW:
-----------------------------------------------------------
George Hammond, M.S. Physics
Email:    ghammond at mediaone.net
Website:  http://people.ne.mediaone.net/ghammond/index.html
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