Structure determines function of the retina, a neural center. 3. Contrast enhancement, directional selectivity, some incomplete circuits.

In Part 3 a circuit for spatial brightness contrast enhancement is analyzed as well as a circuit for generation of directionally selective bipolar cell responses. Several types of bipolar cells with a special function contribute to the complexity of the circuitry of the outer plexiform layer, indicating that the analysis presented in this review only represents the tip of the iceberg.