Notes

There are many structures in the visual system and the majority of them does not give rise to visual perception. We will discuss the conscious vision system.

The retinocortical pathways give rise to conscious vision:

1. Visual field (approx. 180°). The same point is projected onto the nasal and the temporal part of the retina. The retinal image is inverted and reversed right to left compared to the visual field. The less saturated parts (colors) of the visual field are those areas only seen by one eye.
2. The axons of retinal ganglion cells form the optic nerves.
3. At the optic chiasm, axons from the temporal halves of each retina continue into the optic tract on the same side. Axons from the nasal halves cross to the optic tracts on the opposite side. The left hemisphere is analyzed in the right brain hemisphere and viceversa. While the fovea region is represented in both hemispheres.
4. Most axons in the optic tract terminate in the lateral geniculate nucleus.
5. Some axons in the optic tract terminate in the superior colliculus.
6. Axons are sent back and forth between the lateral geniculate and the striate cortex via the optic radiations.
7. Most of the primary visual cortex is on the medial surface of the human brain. It is buried into the calcarine sulcus. And everything below the calcarine sulcus processes the lower quadrant of the visual field.
8. An especially large proportion of primary visual cortex represents the foveal region.
9. The left primary visual cortex gets input from both eyes, but only from the right visual field.