Optic tract

Brain: Optic tract
The left optic nerve and the optic tracts.
Latin	tractus opticus
Gray's	subject #189 814
Part of	Visual system
NeuroNames	hier-443
NeuroLex ID	birnlex_1684

The optic tract is a part of the visual system in the brain.

It is a continuation of the optic nerve and runs from the optic chiasm (where half of the information from each eye crosses sides, and half stays on the same side) to the lateral geniculate nucleus.

Right vs. left

The relationships of the retinal fibers to the optic tracts are illustrated below, with the nasal retinal fibers in blue and the temporal retinal fibers in red.

Click for a larger image.

optic tract	temporal retinal fibers	nasal retinal fiber
right optic tract	from the right eye	from the left eye
left optic tract	from the left eye	from the right eye

In split-brain patients whom have undergone a corpus callosotomy (usually to treat severe epilepsy) the information from one optic tract does not get transmitted to both hemispheres. In carefully controlled experiments, split brain patients shown an image in his or her left left visual field (that is, the left half of what both eyes see), will be unable to vocally name what he or she has seen as the speech-control center is in the left brain hemisphere in most people. See the main article, split-brain.

Pathology

A lesion in the left optic tract will cause right-sided homonomous hemianopsia.

Additional images

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  Diagram of hippocampus

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  Schematic diagram of the primate lateral geniculate nucleus.

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  Superficial dissection of brain-stem. Ventral view.

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  Coronal section of brain through intermediate mass of third ventricle.

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  Hind- and mid-brains; postero-lateral view.

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  Scheme showing central connections of the optic nerves and optic tracts.

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  Base of brain.

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  Section of brain showing upper surface of temporal lobe.

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  Dissection showing the course of the cerebrospinal fibers.

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  Human brainstem anterior view

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  Optic tract and optic nerve