Distal Stimulus: A distant stimulus, as opposed to the proximal, or near, stimulus. An object, such as a tree, which reflects light waves, is a distal stimulus with respect to the eye.
Proximal Stimulus: A near stimulus that acts directly on an aspect of the nervous system. The effect of the light waves on the retina of the eye is an example of proximal stimulus.
Retina: The interior rear surface of the eye, containing light-sensitive cells, called photoreceptors, which collect information and transfer it to other parts of the brain for processing and comprehension.
Visual Cortex: The region of the brain's cerebral cortex that processes visual information.