Optic chiasm: X-shaped structure formed by the crossing of the optic nerves in the brain.
Pathways
The images on the nasal sides of each retina cross over to the opposite side of the brain via the optic nerve at the optic chiasm. The temporal images, on the other hand, stay on the same side. This allows the images from either side of the field from both eyes to be transmitted to the appropriate side of the brain, combining the sides together. Beyond the optic chiasm, with crossed and uncrossed fibers, optic nerves become optic tracts. This allows for parts of both eyes that attend to the right visual field to be processed in the left visual system in the brain, and vice versa. This is linked to skin sensation which reaches the opposite side of the body, after reaching the diencephalon (rear forebrain). Decussation is an adaptive feature of frontally oriented eyes and therefore having binocular vision.
Source: http://www.princeton.edu/~achaney/tmve/wiki100k/docs/Optic_chiasm.html
Image via Wikimedia Commons
Frederick Chu, bet you haven't seen this in anatomy yet!
ReplyDeleteNice! You're right, I haven't seen this in anatomy yet. Head and neck anatomy, plus neuro-anatomy, is probably late this semester or next semester. Man, I haven't dissected eyes (and goat eyes, at that) since middle school.
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ReplyDeleteIt's fascinating to see the way the portion that stays on the eye-side for obvious reasons of reaction speed. But it makes me wonder why the rest of the signal crosses to start with. Corina Marinescu do you know how many organisms do the cross-over?
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