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Fig. 7.4. Cortical response and perceived orientation. The V1 responses of the LISSOM orientation map are shown for three oriented Gaussians, at -30^o, 0^o, and +50^o from vertical. As in the activity plots of Figure 6.5, the colors in the response plots (b,d) represent the orientation preference of each activated neuron, and the saturation (i.e. brightness) represents its activation level. The numbers below each of these plots indicate the perceived orientation, computed from orientation and activation values using the vector sum method. These values are also shown using black horizontal lines in histograms (c,e). The initial V1 response (b) is based on the afferent weights only, before the lateral interactions. The initial response histograms (IH; c) show that a broad range of orientations are activated, and that this distribution is approximately centered around the input's orientation. The location of the response in the activity plots corresponds to the location of the pattern on the retina. After settling, the activity is more focused both spatially and in orientation, as seen in the map activity plots (d) and their histograms (SH; e). The perceived orientation remains an accurate estimate of the actual orientation of the input pattern. An animated demo of this process can be seen at ...