Third Eye, Man

[P3D <gosfield@xxxxxxxxxxxxxxxxx>]

Hi

the organ in humans which is our submerged third eye is the pineal gland 
(once thought to be the seat of the soul).  It still responds to photon 
flux, although of course it has no imaging function.  one of the ways we 
adjust to day/light cycles is through the response of the pineal to 
photons which penetrate the skull, causing changes in the secretion of 
the chemical melatonin, which has numerous effects on physiology.

Tumors of the pineal gland, if large enough, specifically affect
(paralyze) the upward gaze (Parinaud syndrome) but do not affect other eye
movements. 

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Most (?all) bees and wasps have small 'occelli' third eyes on the top of 
their heads which specifically respond to the polarization of light, 
allowing navigation on cloudy days when the sun is not directly 
observable.
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The Anableps is the fish with two eyes but two different (split=ana)
refractive regions in each eye.  They live in Southeast Asia, and cruise
on the surface looking for prey above and below.  If i remember correctly,
they are an 'archer' fish which spits water at insects to capture
them--surely requiring pretty good depth perception.  I wonder how we
could demonstrate if they are stereoscopic. If you can get to a Scientific
American index, the Anableps was the subject of a cover article a number 
of years ago.
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further 3d non-photographic musings:

it is generally agreed that insects do not resolve images the way we do,
having far coarser discrimination of shape and detail.  However, many
predatory insects must have exquisite depth perception, such as
dragonflies (we should hope to last as long as they have) which catch
mosquitos on the wing, and hunting wasps which grab cicadas (?in flight). 
I believe some of the larger dragonflies have a particular area of sharper
perception in their enormous compound eyes, somewhat like a fovea. 

Does anyone know if they have truly stereoscopic vision?  If so, then 
stereopsis has been around an awfully long time.


ted
gosfield@xxxxxxxxxxxxxxxxx


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