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Fig. 6.10. Cortical response after a cortical lesion. The settled activity of neurons for the central 70 × 70 region of V1 is shown for the input in Figure 6.9a before the lesion (a), immediately after (b), several hundred adaptation iterations later (c), and after complete reorganization, i.e. in the new dynamic equilibrium (d). The lesioned area is marked as a dotted line in each plot. Immediately after the lesion, the activity spreads out to neurons that were previously strongly inhibited by the lesioned neurons. For instance, most of the activity just below the lesioned area in (b) did not exist in (a). These neurons partially compensate for the loss of function, which is less severe than expected. As lateral connections reorganize (Figure 6.11), this unmasked activity decreases slightly because lateral inhibition increases: For example, the active area just below the lesion becomes narrower and lighter (c). In the long term, after the afferent weights reorganize (Figure 6.12), the activity outside the lesioned area strengthens again (d). Though lateral inhibition is still stronger in the perilesion area, the afferent input overcomes the inhibition, and neurons at the boundary of the lesion become strongly responsive to inputs previously stimulating lesioned neurons. Similar stages are seen in biological lesion experiments (Section 6.1.2; Merzenich et al. 1990).