The front-end visual system — the retina
The visual system is our most important sense. It is estimated that about one quarter of all nerve cells we have in our central nervous system (CNS) is related to vision in some way. The task of the system is not to form an image of the outside world into the brain, but to help us to survive in this world. Therefore it is necessary to perform a substantial analysis of the 2D image as a projection of the 3D world. For this reason there is much more measured than just the spatial intensity distribution. We will see that the front-end visual system measures simultaneously at multiple resolutions, it measures directly (in the scale-space model) derivatives of the image in all directions at least up to fourth order, it measures temporal changes of intensity, the motion and disparity parameters, and the color differential structure. As a consequence, the layout of the receptors on the retina is strikingly different from the 2D pixel arrays in our conventional digital camera’s.
KeywordsVisual System Ganglion Cell Firing Rate Receptive Field Lateral Geniculate Nucleus
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