IUBio Biosequences .. Software .. Molbio soft .. Network News .. FTP

Cross - Wired Eyes

maxwell mmmaxwell at hotmail.com
Tue May 15 09:23:49 EST 2001


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.
Nor is this limited to inversion--any rotational displacement, and even miniaturizations of the perceived world, or alterations in perceived depth, can be acquired as 'normal' stimuli.
There's quite a bit on this, but here's a few refs, and I'm intentionally not including the amphibian studies where germinal eye structures
are surgically inverted, as immaterial to the point, and lest this thread
diverge even more. (<-magical thinking ;~)

McGonigle, B. O., & Flook, J. P. (1978). 
Long-term retention of single and multistate prismatic adaptation by
humans. Nature, 272, 364-366.

Welch, R. B., Bridgeman, B., Anand, S., & Browman, K. E. (1993). Alternating prism exposure causes dual
adaptation and generalization to a novel displacement. 
Perception & Psychophysics, 54, 195-204.

Wallach, H., Moore, M. E., & Davidson, L. (1963). 
Modification of stereoscopic depth perception. 
American Journal of Psychology, 76, 191-204.

Rock, I. (1965). Adaptation to a minified image. 
Psychonomic Science, 2, 105-106.

Gonshor, A. & Melvill Jones, G. (1976). Extreme vestibulo-ocular adaptation induced by prolonged optical reversal
of vision. Journal of Physiology (London), 256, 381-414.

Flook, J. P., & McGonigle, B. O. (1977). Serial adaptation to conflicting prismatic rearrangement effects in monkey
and man. Perception, 6, 15-29.





More information about the Neur-sci mailing list

Send comments to us at biosci-help [At] net.bio.net