Wardle Susan G, Bex Peter J, Cass John, Alais David
School of Psychology, The University of Sydney, Sydney, New South Wales, Australia.
J Vis. 2012 Jun 8;12(6):12. doi: 10.1167/12.6.12.
It is well-established that depth discrimination is finer in the fovea than the periphery. Here, we study the decline in depth discrimination thresholds with distance from the fovea using an equivalent noise analysis to separate the contributions of internal noise and sampling efficiency. Observers discriminated the mean depth of patches of "dead leaves" composed of ellipses varying in size, orientation, and luminance at varying levels of disparity noise between 0.05 and 13.56 arcmin and visual field locations between 0° and 9° eccentricity. At low levels of disparity noise, depth discrimination thresholds were lower in the fovea than in the periphery. At higher noise levels (above 3.39 arcmin), thresholds converged, and there was little difference between foveal and peripheral depth discrimination. The parameters estimated from the equivalent noise model indicate that an increase in internal noise is the limiting factor in peripheral depth discrimination with no decline in sampling efficiency. Sampling efficiency was uniformly low across the visual field. The results indicate that a loss of precision of local disparity estimates early in visual processing limits fine depth discrimination in the periphery.
众所周知，中央凹的深度辨别能力比周边区域更精细。在此，我们使用等效噪声分析来分离内部噪声和采样效率的贡献，研究深度辨别阈值随离中央凹距离的下降情况。观察者辨别由大小、方向和亮度各异的椭圆组成的“枯叶”斑块的平均深度，这些斑块处于0.05至13.56角分的不同视差噪声水平以及0°至9°离心率的视野位置。在低视差噪声水平下，中央凹的深度辨别阈值低于周边区域。在较高噪声水平（高于3.39角分）时，阈值趋于一致，中央凹和周边深度辨别之间几乎没有差异。从等效噪声模型估计的参数表明，内部噪声的增加是周边深度辨别中的限制因素，采样效率没有下降。整个视野的采样效率均较低。结果表明，视觉处理早期局部视差估计精度的丧失限制了周边区域的精细深度辨别。
