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Fig. 5.27. Self-organized OR/OD map. Based on oriented Gaussian patterns with different brightnesses in each eye, LISSOM develops realistic orientation (a) and ocular dominance (b) maps in the same area of cortex. The orientation map features are outlined in (a), (c) and (d) as in Figure 2.4. In (c), the orientation preferences are overlaid with the ocular dominance gradient: High gradient (black) marks the boundary between OD stripes. These boundaries rarely overlap pinwheel centers or fractures, they intersect OR boundaries in linear zones at right angles, and they rarely follow OR boundaries. These relationships are further highlighted in (d), where regions of low orientation selectivity (pinwheel centers and fractures) are plotted in dark gray, overlaid with the ocular dominance boundaries. Again, these features rarely intersect, suggesting that the map organization results from distributing selectivity for different features evenly across the cortex. Similar interaction between orientation and ocular dominance is seen in biological maps (Figure 5.3; Blasdel 1992b).