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Fig. 11.4. Self-organized orientation map. The orientation preference and selectivity of each neuron in SMAP and GMAP are plotted using the same conventions as in Figure 5.9. Because of the intracolumnar connections, the two maps develop similar organizations. As in LISSOM and in biological maps (Figures 2.5 and 5.9), the preferences change smoothly across the cortex, and exhibit features such as linear zones, pairs of pinwheels, saddle points, and fractures (outlined as in Figure 2.4). As in animal maps, the neurons at the pinwheel centers and fractures are unselective for orientation (these features are more prominent in the SMAP, which drives the self-organization). The orientation histograms are essentially flat and therefore free of artifacts. These plots show that realistic orientation maps can be formed with spiking neurons and with the SG model of cortical columns.