Szinte Martin, Wexler Mark, Cavanagh Patrick
Laboratoire Psychologie de la Perception, Université Paris Descartes, Sorbonne Paris Cité, Paris, France.
J Vis. 2012 Jul 24;12(7):12. doi: 10.1167/12.7.12.
Different attention and saccade control areas contribute to space constancy by remapping target activity onto their expected post-saccadic locations. To visualize this dynamic remapping, we used a technique developed by Honda (2006) where a probe moved vertically while participants made a saccade across the motion path. Observers do not report any large excursions of the trace at the time of the saccade that would correspond to the classical peri-saccadic mislocalization effect. Instead, they reported that the motion trace appeared to be broken into two separate segments with a shift of approximately one-fifth of the saccade amplitude representing an overcompensation of the expected retinal displacement caused by the saccade. To measure the timing of this break in the trace, we introduced a second, physical shift that was the same size but opposite in direction to the saccade-induced shift. The trace appeared continuous most frequently when the physical shift was introduced at the midpoint of the saccade, suggesting that the compensation is in place when the saccade lands. Moreover, this simple linear shift made the combined traces appear continuous and linear, with no curvature. In contrast, Honda (2006) had reported that the pre- and post-saccadic portion of the trace appeared aligned and that there was often a small, visible excursion of the trace at the time of the saccade. To compare our results more directly, we increased the contrast of our moving probe in a third experiment. Now some observers reported seeing a deviation in the motion path but the misalignment remained present. We conclude that the large deviations at the time of saccade are generally masked for a continuously moving target but that there is nevertheless a residual misalignment between pre- and post-saccadic coordinates of approximately 20% of the saccade amplitude that normally goes unnoticed.
不同的注意力和扫视控制区域通过将目标活动重新映射到预期的扫视后位置来实现空间恒常性。为了可视化这种动态重新映射，我们使用了本田（2006年）开发的一种技术，即当参与者在运动路径上进行扫视时，一个探针垂直移动。观察者在扫视时并未报告任何与经典的扫视周围定位错误效应相对应的轨迹大幅偏移。相反，他们报告说运动轨迹似乎被分成了两个独立的部分，有一个大约扫视幅度五分之一的偏移，这代表了对扫视引起的预期视网膜位移的过度补偿。为了测量轨迹中断的时间，我们引入了第二个物理偏移，其大小与扫视引起的偏移相同，但方向相反。当在扫视中点引入物理偏移时，轨迹最常看起来是连续的，这表明在扫视着陆时补偿就已到位。此外，这种简单的线性偏移使组合后的轨迹看起来是连续且线性的，没有曲率。相比之下，本田（2006年）曾报告说，轨迹的扫视前和扫视后部分看起来是对齐的，并且在扫视时轨迹经常会有一个小的、可见的偏移。为了更直接地比较我们的结果，我们在第三个实验中提高了移动探针的对比度。现在一些观察者报告看到运动路径有偏差，但错位仍然存在。我们得出结论，对于连续移动的目标，扫视时的大幅偏差通常会被掩盖，但扫视前和扫视后坐标之间仍存在约扫视幅度20%的残余错位，这通常未被注意到。
