Optic_chiasm

The optic chiasma (Greek χίασμα, "crossing", from the Greek χλαζειν \'to mark with an X\', after the Greek letter \'Χ\', chi) is the part of the brain where the optic nerves partially cross.

Pathways

Specifically, in the optic chiasm, the nerves connected to the right eye that attend to the right temporal visual field (located in the right retina) cross to the left half of the brain, while the nerves from the left eye that attend to the left temporal visual field (located in the left retina) cross to the right half of the brain.

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.

Optic chiasm in cats

In Siamese cats with certain genotypes of the albino gene, this wiring is disrupted, with less of the nerve-crossing than is normal, as a number of scholars have reported. OMIA To compensate for lack of crossing in their brains, they cross their eyes (strabismus). R. W. Guillery; J. H. Kaas. Genetic Abnormality of the Visual Pathways in a "White" Tiger. Science. 1973 Jun 22;180(92):1287-9. GS

This is also seen in albino tigers, as Guillery & Kaas report.Guillery, R. Visual pathways in albinos. Scientific American 1974 May;230(5):44-54. PubMed

Additional images

References

• Jeffery, Glen. Architecture of the Optic Chiasm and the Mechanisms That Sculpt Its Development Physiol Rev, Oct 2001; 81: 1393 - 1414.

External links

• Roche Lexicon - illustrated navigator, at Elsevier 13048.000-1

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