An example of bottom up processing occurs in vision. Bottom-up processing beings with transduction, which is the conversion of stimulus energy into neural impulses. The stimulus energy is in the form of light energy (waves), and this light energy enters the eye. After passing through such parts as the iris and the lens, the light energy reaches the retina, where sense receptors are located and where transduction occurs. Rods and cones are the eye's sense receptors that produce chemical changes that generate neural signals. These neural signals get relayed to the optic nerve, which leads to the brain.
Another example of bottom-up processing is that which occurs in hearing. Like vision, the stimulus energy that enters the ears is in the form of waves. These sound waves travel through the outer, middle and inner ear until they finally vibrate the basilar membrane. The hair cells on this membrane trigger impulses in nerve fibers that form the auditory nerve that relays this information to the brain.
Top-down processing is the information processing guided by higher-level mental processes, as when we construct perceptions drawing on our experience and expectations. Top down processing is the mind interpreting what our senses detect. Without top-down processing, one would be able to see someone's face, but not recall that person's name or remember him or her. This processing is akin to perception, which is the process of organizing and interpreting sensory information. Top-down processing is especially important in the "interpretation" aspect of