Patel Saumil S, Bedell Harold E, Tsang Dorcas K, Ukwade Michael T
Department of Neurobiology and Anatomy, University of Texas Medical School at Houston, Houston, Texas 77030, USA.
J Opt Soc Am A Opt Image Sci Vis. 2009 Apr;26(4):847-61. doi: 10.1364/josaa.26.000847.
We seek to determine the relationship between threshold and suprathreshold perception for position offset and stereoscopic depth perception under conditions that elevate their respective thresholds. Two threshold-elevating conditions were used: (1) increasing the interline gap and (2) dioptric blur. Although increasing the interline gap increases position (Vernier) offset and stereoscopic disparity thresholds substantially, the perception of suprathreshold position offset and stereoscopic depth remains unchanged. Perception of suprathreshold position offset also remains unchanged when the Vernier threshold is elevated by dioptric blur. We show that such normalization of suprathreshold position offset can be attributed to the topographical-map-based encoding of position. On the other hand, dioptric blur increases the stereoscopic disparity thresholds and reduces the perceived suprathreshold stereoscopic depth, which can be accounted for by a disparity-computation model in which the activities of absolute disparity encoders are multiplied by a Gaussian weighting function that is centered on the horopter. Overall, the statement "equal suprathreshold perception occurs in threshold-elevated and unelevated conditions when the stimuli are equally above their corresponding thresholds" describes the results better than the statement "suprathreshold stimuli are perceived as equal when they are equal multiples of their respective threshold values."
我们试图确定在提高位置偏移和立体深度感知各自阈值的条件下，阈值与超阈值感知之间的关系。使用了两种提高阈值的条件：（1）增加行间间隙，（2）屈光性模糊。尽管增加行间间隙会大幅提高位置（游标）偏移和立体视差阈值，但超阈值位置偏移和立体深度的感知保持不变。当通过屈光性模糊提高游标阈值时，超阈值位置偏移的感知也保持不变。我们表明，超阈值位置偏移的这种归一化可归因于基于地形图的位置编码。另一方面，屈光性模糊会增加立体视差阈值并降低超阈值立体深度的感知，这可以通过一个视差计算模型来解释，在该模型中，绝对视差编码器的活动乘以一个以水平视野为中心的高斯加权函数。总体而言，“当刺激同样高于其相应阈值时，在阈值提高和未提高的条件下会出现相等的超阈值感知”这一表述比“当超阈值刺激是其各自阈值的相等倍数时，它们被感知为相等”这一表述更能描述结果。
