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Fig. 10.14. Example postnatal training presentations. The top row shows six randomly generated images drawn on the retina during postnatal learning. Each image contains a foreground item chosen randomly from the images in Figure 10.13. The foreground item was overlaid onto a random portion of an image from a database of 58 natural scenes (National Park Service 1995), at a random location and at a nearly vertical orientation (drawn from a normal distribution around vertical, with &sigma = &pi / 36 radians). The second row shows the LGN response to each of these sample patterns, and the bottom row the FSA response at the start of postnatal training. The FSA responds to groups of dark spots on the retina, such as the eyes and mouths in (b), (c), and (f) and the horse's dark markings in (d). Subsequent learning in the FSA will be driven by these patterns of activity. Because the prenatal training biases the activity patterns toward faces, postnatal self-organization will also be biased toward faces, as is shown in Figure 10.15.