Caption: Brain and eye anatomy. Computer artwork of the brain from below, with the front of the brain and the eyeballs (both sectioned) at top. Nerves (yellow) include the optic nerves, the olfactory nerves (between the optic nerves), and the upper part of the spinal cord (lower centre). The cerebellum has been removed, and the brain made transparent to show the limbic structures (centre). The brainstem is above the spinal cord. At bottom are the occipital lobes (red), the visual processing centres at the rear of the brain. The optic nerves cross at the optic chiasma (centre), allowing the images from both eyes to be combined.

Credit: SPRINGER MEDIZIN/SCIENCE PHOTO LIBRARY