visual pathway

visual pathway,

a pathway over which a visual sensation is transmitted from the retina to the brain. A pathway consists of an optic nerve, the fibers of an optic nerve traveling through the optic chiasm to the lateral geniculate body of the thalamus, and optic radiations terminating in an occipital lobe. Each optic nerve contains fibers from only one retina. The optic chiasm contains fibers from the nasal parts of the retinas of both eyes. These fibers cross to the opposite side of the brain at the optic chiasm. The fibers from the temporal part of each eye do not cross at the optic chiasm, pass through the lateral geniculate body on the same side of the brain, and continue back to the occipital lobe. Thus the optic tracts, occipital lobe, lateral geniculate bodies of the thalamus, and optic chiasm each contain nerve fibers from both eyes. If the right optic tract were destroyed, a person would lose partial vision in both eyes-the right nasal and the left temporal fields of vision.

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visual

pertaining to vision.

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visual acuity test

performed by walking the animal through an obstacle course. A room full of unfamiliar furniture, or a stairway is usually used for companion animals. Farm animals are led or driven through a passage with drums or boxes strewn across it.

visual cortex

the part of the cerebral cortex which deals with images received by the visual apparatus.

visual evoked potentials (VEPs)

see visual evoked response.

visual following

movement of the eyes in watching a moving object.

visual pathway

the bulk of the retinal ganglion cells have axons in the optic nerve which synapse with cells in the lateral geniculate nucleus in the thalamus, which project to the visual cortex in the occipital lobe of the cerebrum; in a secondary visual pathway the axons of the remainder of the retinal ganglion cells terminate in the anterior rostral colliculus (pretectal region).

visual system

includes the eye, the optic nerve and the optic cortex in the cerebrum. The oculomotor, trochlear, abducent, trigeminal and facial nerves are all involved in reflexes which are part of the animal's responses to visual stimuli.

visual yellow

all-trans retinal; see retinal (2).