Vision, visual memories The primary visual cortex (V1) is found in the occipital lobe at the back of the brain.
The occipital lobe is demarcated by the occipital bone, marking boundaries with the parietal lobe in front and the temporal lobe to the side. Our visual field is topographically mapped to V1. Retinal signals travel along the optic nerve through the optic chiasm, where they split—those from the center visual field traverse the optic tract to reach V1 areas in both hemispheres, while those from our outer visual field reach the opposite hemisphere only. Before signals reach V1, they also go through the lateral geniculate nucleus of the thalamus. The signals leave the lateral geniculate nucleus and reach V1 through the optic radiation. Two streams of visual processing then leave V1 in forward projections. The dorsal stream—the “where” stream—goes to the parietal lobe and is for locating objects and visually guided action. The ventral stream—the “what” stream—goes to the temporal lobe and is for recognizing objects.
Human vision depends on many neural streams of activation that the brain combines in perception. If something goes wrong in the neural streams of vision, strange things can happen to this binding process and a person might, for instance, perceive floating colors instead of colored objects, flickering images instead of fluid motion, a reduced visual field, and so on. Many odd cases have been reported in the literature on visual perception. The visual system is complex and involves nearly half of the cortex.