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Fig. 6.11. Reorganization of lateral inhibitory weights after a cortical lesion. The lateral inhibitory weights of a neuron at the bottom-left corner of the lesion are plotted in gray scale from white to black (low to high; orientation preferences or selectivity are not shown). The small white square marks the neuron and the jagged black outline indicates the connectivity before self-organization and pruning, as in Figure 5.12. (a) The connections before the lesion follow the neuron's orientation preference as usual. (b) Through Hebbian adaptation after the lesion, the connections from neurons in the lesioned area approach zero, because those neurons are no longer active. Because the total inhibitory weight is kept constant by weight normalization, the inhibition concentrates in the connections outside the lesioned zone. This inhibition decreases the responses of the perilesion neurons, giving a computational account for the regressive phase in biology (Section 6.1.2; Merzenich et al. 1990).