Bahcall D O, Kowler E
Department of Psychology, Rutgers University, Piscataway, New Jersey 08854, USA.
Nature. 1999 Aug 26;400(6747):864-6. doi: 10.1038/23693.
A central problem in human vision is to explain how the visual world remains stable despite the continual displacements of the retinal image produced by rapid saccadic movements of the eyes. Perceived stability has been attributed to 'efferent-copy' signals, representing the saccadic motor commands, that cancel the effects of saccade-related retinal displacements. Here we show, by means of a perceptual illusion, that traditional cancellation theories cannot explain stability. The perceptual illusion was produced by first inducing adaptive changes in saccadic gain (ratio of saccade size to target eccentricity). Following adaptation, subjects experienced an illusory mislocalization in which widely separated targets flashed before and after saccades appeared to be in the same place. The illusion shows that the perceptual system did not take the adaptive changes into account. Perceptual localization is based on signals representing the size of the initially-intended saccade, not the size of the saccade that is ultimately executed. Signals representing intended saccades initiate a visual comparison process used to maintain perceptual stability across saccades and to generate the oculomotor error signals that ensure saccadic accuracy.
人类视觉中的一个核心问题是解释尽管眼睛快速扫视运动产生的视网膜图像不断位移，但视觉世界如何保持稳定。感知稳定性被归因于“传出副本”信号，该信号代表扫视运动命令，可抵消与扫视相关的视网膜位移的影响。在这里，我们通过一种感知错觉表明，传统的抵消理论无法解释稳定性。这种感知错觉是通过首先诱导扫视增益（扫视幅度与目标偏心度的比率）的适应性变化而产生的。适应之后，受试者经历了一种虚幻的定位错误，即扫视前后闪烁的相距甚远的目标似乎在同一位置。这种错觉表明，感知系统没有考虑适应性变化。感知定位基于代表最初预期扫视幅度的信号，而不是最终执行的扫视幅度。代表预期扫视的信号启动一个视觉比较过程，该过程用于在扫视过程中保持感知稳定性，并生成确保扫视准确性的眼动误差信号。
