1. Visual Processing Processing in the Retina
On Center and Off Center Cells
Higher Levels of Processing
Neural Pathways
Edge Effects
Motion Illusions
Perceptual Learning and Ambiguity

3. Optical Processing
Level one processing occurs in the retina, the rods and cones are the first order cells, bipolar cells are 2nd order and ganglionic cells are the third. Amacrine cells and horizontal cells create both converging and diverging pathways.
Rods and cones hyperpolarize when stimulated and Na channels close
Horizontal cells produce graded hyperpolarizations
Some bipolar cells hyperpolarize and some depolarize
Some ganglionic cells hyperpolarize and some depolariize.
Ganglionic cells are matched to their bipolar cells
Amacrine cells respond transiently when the stimulus changes

4. Each ganglionic cell has a particular area of the retina that it receives information from. These visual fields are circular. The fields near the fovea are quite small so visual acuity is great.
The fields are divided into two areas -- a center and a surround. There are two types of fields an on center field and an off center field.
Off CenterInhibited when light in center, fires when light in surround
On Cell Ganglion responds when light in center, inhibited by light in surround

7. Film Clip on Processing

8. First order – rods and cones
Second – bipolar cells
Third – ganglionic cells
Fourth – neurons of the lateral geniculate nucleus
Fifth – Simple cells of the visual cortex
Sixth – Complex cells of the cortex (Brodman’s Area 17)

24. Simple Cell and Motion Illusions