Heeley D W, Buchanan-Smith H M
Department of Psychology, University of St Andrews, Fife, Scotland.
Vision Res. 1992 Jan;32(1):97-104. doi: 10.1016/0042-6989(92)90117-2.
Orientation discrimination thresholds were estimated for symmetrical "plaids", constructed by the super-imposition of two, independent drifting sine-wave gratings of 2.5 c/deg. Experiments were conducted when the apparent direction of drift was on the two principal meridians (vertical and horizontal), and when the apparent direction of drift was at the two oblique orientations (45 and 135 deg). Acuity for the direction of drift for these stimuli is of the same order of precision as orientation acuity for static or drifting gratings, and exhibits a meridional anisotropy that favours the principal meridians. This anisotropy follows a pattern that is determined by the apparent direction of drift, and not the orientation of the underlying elements. Acuity for orientation is lowest for oblique drift directions, even though both of the elements are oriented on the principal meridians. This finding was confirmed when the orientation of the underlying elements was subject to a random variation. The results are not easily accommodated by models that propose that the individual elements of the plaid are analysed separately. Second, the data are incompatible with models of the oblique effect of orientation discrimination that are based on an axis dependent, differential sampling of the retinal image.
通过叠加两个2.5周/度的独立漂移正弦波光栅构建对称“方格图案”，并估计其方向辨别阈值。实验在漂移的视在方向位于两个主要子午线（垂直和水平）时进行，以及在漂移的视在方向处于两个倾斜方向（45度和135度）时进行。这些刺激的漂移方向敏锐度与静态或漂移光栅的方向敏锐度具有相同的精度顺序，并且表现出有利于主要子午线的子午线各向异性。这种各向异性遵循由漂移的视在方向而非底层元素的方向决定的模式。即使两个元素都沿主要子午线定向，倾斜漂移方向的方向敏锐度也是最低的。当底层元素的方向受到随机变化影响时，这一发现得到了证实。提出对方格图案的各个元素进行单独分析的模型不容易解释这些结果。其次，这些数据与基于视网膜图像的轴依赖性差异采样的方向辨别倾斜效应模型不兼容。
