Function of optic chiasma??

Charles E. Weaver wheat at mbcrrc.bu.edu
Tue Jan 3 09:53:30 EST 1995


In article <D19I4o.I5s at hkuxb.hku.hk>, h9309857 at hkusub (Anselm Mak) wrote:

> Can anyone tell me the use of the optic chiasma??  What is the
> sigificance of transmitting the left visual field to the right calcarine
> sulcus and vice veras??
>
     I am not sure if anyone can give a definitive answer to this
question.....I would note though that contralateral control/representation
is pretty much the rule in brain function.....eg  the major portion of the
motor control of the right side is carried out by the left side of the
brain.....the same goes for sensory modalities...vision included.  An
important point is that there is some ipsilateral contribution in most of
cases (one notable exception is that in the rabit the optic nerves are
totally contralateral....in humans this is not the case there is as you
have noted.....crossing) anyway this dosen't answer your question other
than to note that in general the left side of the brain handles the right
side of the body including the right visual field and visa versa for the
left brain.
     Perhaps there is some adaptive advantage such that if one incures
damage to the right optic lobe you only loose the left visual field, but
maintain partial function in both eyes.....stereo vision in one half the
field may be better than as would be the case for the rabit total vision
loss in one eye (the way the eyes of the rabit are set I don't think
stereo vision is something they would worry about).

.....just my two cents.....or mayby my nickle

-Chuck

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\\^//   Charles E.Weaver
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