Fredericksen R E, Verstraten F A, van de Grind W A
McGill Vision Research Unit, Montreal, Quebec, Canada.
Vision Res. 1997 Jan;37(1):99-119. doi: 10.1016/s0042-6989(96)00074-0.
A number of psychophysical investigations have used spatial-summation methods to estimate the receptive field (RF) geometry of motion detectors by exploring how psychophysical thresholds change with stimulus height and/or width. This approach is based on the idea that an observer's ability to detect motion direction is strongly determined by the relationship between the stimulus geometry (height and width) and the RF of the activated motion detectors. Our results show that previous estimates of RF geometry can depend significantly on stimulus position in the visual field as well as on the stimulus height-to-width ratio. The data further show that RF estimates depend on the stimulus in a manner that is inconsistent with basic predictions derived from current motion detector models. Hence previous estimates of height, width, and height-to-width ratios of motion detector RFs are inaccurate and unreliable. This inaccuracy/unreliability is attributed to a number of sources. These include incorrect fixed-parameter values in model fits, as well as the confounding of physiological spatial summation area through combined use of contrast thresholds and Gaussian-windowed stimuli. A third source of error is an asymmetric variation of spatiotemporal correlation in the stimulus as either its height or width is varied (and the other dimension held constant). Most importantly, a fourth source of unreliability is attributed to the existence of a nonlinear, nonmonotonic distribution of motion detectors in the visual field that has been previously described and is a natural result of visual anatomy.
许多心理物理学研究通过探究心理物理学阈值如何随刺激高度和/或宽度变化，使用空间总和方法来估计运动探测器的感受野（RF）几何形状。这种方法基于这样一种观点，即观察者检测运动方向的能力在很大程度上取决于刺激几何形状（高度和宽度）与激活的运动探测器的RF之间的关系。我们的结果表明，先前对RF几何形状的估计可能在很大程度上取决于视野中的刺激位置以及刺激的高宽比。数据进一步表明，RF估计对刺激的依赖方式与当前运动探测器模型得出的基本预测不一致。因此，先前对运动探测器RF的高度、宽度和高宽比的估计是不准确且不可靠的。这种不准确/不可靠归因于多种来源。这些包括模型拟合中不正确的固定参数值，以及通过结合使用对比度阈值和高斯窗口化刺激对生理空间总和区域的混淆。第三个误差来源是当刺激的高度或宽度变化（而另一个维度保持不变）时，刺激中时空相关性的不对称变化。最重要的是，第四个不可靠来源归因于视野中存在先前已描述的运动探测器的非线性、非单调分布，这是视觉解剖学的自然结果。
