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Fig. 6.8. Dynamic RF expansion and perceptual shift after a retinal scotoma. In the top row, the response of the network to a single vertical input across the bottom edge of the retinal scotoma (a) is shown before the lesion (b) and after the cortex reorganized and the scotoma was removed (c). The lower activity patch, due to neurons just outside the cortical scotoma, has almost disappeared in the reorganized response, because these neurons now prefer horizontal inputs (as seen in the OR map of Figure 6.7c). As a result, these neurons do not inhibit the neurons inside the scotoma as strongly as before, and the inside neurons now have larger effective RFs, as indicated by the slightly larger and more intense top activity patch. The inward perceptual shift is most clearly seen when the input is just outside the retinal scotoma and parallel to its boundary, like the horizontal input below the scotoma in the bottom row. The reorganized response is much larger than the initial response because most neurons near the bottom boundary now prefer horizontal inputs. In addition, the RFs of these neurons have shifted outward (as seen in the retinotopy plot of Figure 6.7c), which results in a corresponding small shift of the response pattern inward. These results replicate the dynamic RF size expansion and the corresponding inward shift in the perceived location found in biological experiments (Section 6.1.1; Kapadia et al. 1994; Pettet and Gilbert 1992); the magnification of boundary orientations is a prediction of the model.