Tripathy S P, Levi D M, Ogmen H
College of Optometry, University of Houston, TX 77204-6052, USA.
Vision Res. 1996 Jun;36(11):1585-96. doi: 10.1016/0042-6989(95)02200-7.
Three competing hypotheses have been proposed for the cortical representation of the blind spot. These are: (i) the regions surrounding the blind spot maintain their spatial values; (ii) the opposite sides of the blind spot are represented adjacently at the cortex, so that the blind spot is "sewn-up"; and (iii) the blind spot is sewn-up with compensation occurring in the immediate surround of the blind spot, so that spatial values are distorted only in the immediate surround of the blind spot. To distinguish between these hypotheses we used a two-dot alignment task, with the two dots straddling the blind spot at varying dot separations. Thresholds in the two-dot alignment task are limited by the cortical separation of the two dots. When thresholds for alignment across the blind spot are compared with thresholds over intact retina at the same eccentricity, the three hypotheses predict: (i) no change in thresholds; (ii) a lowering of thresholds; and (iii) a lowering of thresholds but only at separations slightly greater than the diameter of the blind spot. Thresholds across the blind spot were closely similar to thresholds across intact retina. The results do not support a sewing-up (with or without compensation) of the blind spot. Rather, our results are consistent with a preservation of spatial values around the blind spot.
针对盲点的皮层表征，已提出三种相互竞争的假说。它们分别是：（i）盲点周围的区域保持其空间值；（ii）盲点的相对两侧在皮层上相邻表征，从而使盲点被“缝合”；（iii）盲点被缝合，且在盲点的紧邻周边区域发生补偿，使得空间值仅在盲点的紧邻周边区域发生扭曲。为区分这些假说，我们使用了双点对齐任务，两个点以不同的点间距横跨盲点。双点对齐任务中的阈值受两点在皮层上的间距限制。当将横跨盲点的对齐阈值与相同偏心率下完整视网膜上的阈值进行比较时，这三种假说预测：（i）阈值无变化；（ii）阈值降低；（iii）阈值降低，但仅在间距略大于盲点直径时。横跨盲点的阈值与横跨完整视网膜的阈值非常相似。这些结果不支持盲点的“缝合”（无论有无补偿）。相反，我们的结果与盲点周围空间值的保留一致。
