Visual Mechanism

This cross section of a brain, as viewed from above, shows how the image which reaches the retina is coded and relayed to the visual cortex. Light falling on the retina stimulates the fibers of the optic nerve. These fibers join to form a cross, called the optic chiasma, where fibers from the inner side of each eye pass to the visual cortex on the opposite side. Fibers from the outer field of each eye are uncrossed, passing to the visual cortex on the same side. From the optic chiasma, the information passes, via the optic tracts, to the lateral geniculate bodies, where perception of depth occurs, and then onto the optic radiation, which transmits the information to the primary visual cortex, situated in the occipital lobes. The primary visual cortex is responsible for the perception of the position of objects in space, and their relationship to each other, as well as the perception of light and shade. In this way, an overall composite picture of any object is formed.