The occipital lobe is more nearly a structural and functional entity than are any of the other cerebral lobes. All of its functions are concerned either directly or indirectly with vision. The visual receptive area is located on the lips of the calcarine fissure and adjacent portions of the cuneus and lingual gyrus, and extends around the occipital pole to occupy a portion of the lateral surface of the hemisphere. The optic radiations pass from the lateral geniculate body to the striate cortex on the upper and lower lips of the calcarine fissure. Stimulation, or irritation, of the calcarine cortex produces unformed visual hallucinations, such as fotomas and flashes of light, in the corresponding fields of vision. Destructive lesions result in defects in the visual fields supplied by the affected areas. Bilateral lesion may result in cortical blindness. Unilateral lesions may result in contralateral hemianopia or quadrantanopia.