Prince S, Offen S, Cumming B G, Eagle R A
University Laboratory of Physiology, University of Oxford, Parks Road, Oxford OX1 3PT, UK.
Perception. 2001;30(3):367-80. doi: 10.1068/p3049.
We examine how differently oriented components contribute to the discrimination of motion direction along a horizontal axis. Stimuli were two-frame random-dot kinematograms that were narrowband filtered in spatial frequency. On each trial, subjects had to state whether motion was to the left or the right. For each stimulus condition, Dmax (the largest displacement supporting 80% correct direction discrimination performance) was measured. In experiment 1, Dmax was measured for orientationally narrowband stimuli as a function of their mean orientation. Dmax was found to increase as the orientation of the stimuli became closer to the axis of motion. Experiment 2 used isotropic stimuli in which some orientation bands contained a coherent motion signal, and some contained only noise. When the noise band started at vertical orientations and increased until only horizontal orientations contained a coherent motion signal, Dmax increased slightly. This suggests that near-vertical orientations interfere with motion perception at large displacements when they contain a coherent motion signal. When the noise band started at horizontal and increased until only vertical orientations contained the motion signal, Dmax decreased steadily. This implies that Dmax depends at least partly on the most horizontal motion signal in the stimulus. These results were contrasted with two models. In the first, the visual system utilises the most informative orientations (nearest horizontal). In the second, all available orientations are used equally. Results supported an intermediate interpretation, in which all orientations are used but more informative ones are weighted more heavily.
我们研究了不同方向的成分如何有助于沿水平轴的运动方向辨别。刺激物是在空间频率上进行窄带滤波的两帧随机点运动图。在每次试验中，受试者必须说明运动是向左还是向右。对于每种刺激条件，测量了Dmax（支持80%正确方向辨别性能的最大位移）。在实验1中，测量了定向窄带刺激的Dmax作为其平均方向的函数。发现随着刺激物的方向变得更接近运动轴，Dmax会增加。实验2使用了各向同性刺激，其中一些方向带包含连贯运动信号，一些只包含噪声。当噪声带从垂直方向开始并增加，直到只有水平方向包含连贯运动信号时，Dmax略有增加。这表明当近垂直方向包含连贯运动信号时，在大位移时会干扰运动感知。当噪声带从水平方向开始并增加，直到只有垂直方向包含运动信号时，Dmax稳步下降。这意味着Dmax至少部分取决于刺激中最水平的运动信号。这些结果与两个模型进行了对比。在第一个模型中，视觉系统利用最具信息性的方向（最接近水平方向）。在第二个模型中，所有可用方向被平等使用。结果支持了一种中间解释，即所有方向都被使用，但更具信息性的方向权重更大。
