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Why does the lateral geniculate nucleus have layers linked to different eyes?

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Diagram of a human brain showing a median sagittal section, highlighting the fourth ventricle and cerebellum in the hindbrain, with labeled anatomical structures including the pons, medulla oblongata, and central canal of the spinal cord. — thalamus Sagittal section of the human brain, showing structures of the cerebellum, brainstem, and cerebral ventricles.

The lateral geniculate nucleus (LGN) is organized into six distinct layers to maintain the segregation of visual information arriving from the two eyes. Specifically, the crossed fibers from the retina relay in layers 1, 4, and 6, while the uncrossed fibers relay in layers 2, 3, and 5.12

This laminar structure ensures that impulses from the left and right eyes remain separate at the level of the LGN. Because of this anatomical arrangement, it is rare to find geniculate neurons that respond to stimuli from both eyes simultaneously. By keeping these inputs distinct, the LGN acts as a relay station that preserves retinotopic organization—representing both the specific eye of origin and the location of the input within the visual field—before the information is projected to the primary visual cortex. It is only once these signals reach the cortex that they are integrated by common neurons to facilitate processes such as depth perception.1234