Figure 8.

Angioscotomas cause only slight changes to OR maps induced indirectly by the tendency for the OD and OR contours to intersect orthogonally. A–G, OR maps are shown as contour maps (contours in blue) and false-color maps in which intensity indicates strength of OR selectivity and color indicates OR preference according to the color code shown at bottom right. OD contours are overlaid in black or white. The crosses indicate the cortical locations of the feature points that are deprived after birth. The angioscotoma was introduced at birth time K_b, and annealing was continued at the same rate for 10 iterations after birth; a smaller K_b value corresponds to later birth (and hence angioscotoma introduction), when column formation is more advanced. A–C, OD columns form slightly before OR columns (l = 0.05; r = 0.07; see Materials and Methods). If the angioscotoma is introduced at an appropriate time to be represented in the OD map and the OR map has formed (B), then OR columns are affected indirectly by the angioscotoma, because they must arrange themselves in a way that maintains the tendency for the OD and OR contours to intersect orthogonally. E–G, OR columns form slightly before OD columns (l = 0.05; r = 0.075). If the OR columns have already formed and the angioscotoma is introduced at an appropriate time to be represented in the OD map (E,F), then the OD contours are more convoluted, because the OD columns must arrange themselves in a way that maintains the tendency for the OD and OR columns to intersect orthogonally. H, The small effect of the angioscotoma on the OR map in B can be seen when the OR contours of the map that develops with the angioscotoma (blue) are overlaid on the contours of the OR map that develops if the angioscotoma is not introduced (red). I, When a wider angioscotoma is introduced, the effect on the OR map is larger.