Raymond J, Braddick O
School of Psychology, University of Wales, Bangor, Gwynedd, U.K.
Vision Res. 1996 Jul;36(13):1931-7. doi: 10.1016/0042-6989(95)00241-3.
Opponency between opposite directions of motion is a characteristic of many models of movement detection and is commonly invoked in explanations of the motion after-effect. If detection of opposite directions is mediated by a single mechanism, then a single, smooth psychometric function for the discrimination of global direction in random-dot kinematograms should be found as a function of the percent of directional coherence of dots in the display, ranging from 100% coherence leftwards through 0% coherence to 100% coherence rightwards. Moreover, after rightward motion adaptation, a single psychometric function should still be observed if adaptation affects the perceptual system prior to opponent interactions. If, however, leftward and rightward detectors operate independently, then the slopes of the leftward and rightward halves of the function may differ, particularly after unidirectional adaptation. We measured the probability of a "rightward" direction response for nine values of motion coherence for five observers with and without prior rightward motion adaptation. Although a smooth psychometric function was found without motion adaptation, after adaptation, the rightward half of the psychometric function was flattened whereas the leftward half remained unchanged. Such results indicate that movement direction analysers operate in a non-opponent manner.
运动方向相反之间的拮抗作用是许多运动检测模型的一个特征，并且在运动后效的解释中经常被提及。如果相反方向的检测是由单一机制介导的，那么对于随机点运动图中全局方向的辨别，应该能找到一个单一的、平滑的心理测量函数，它是显示中具有方向一致性的点的百分比的函数，范围从100%向左一致性到0%一致性再到100%向右一致性。此外，如果适应在拮抗相互作用之前影响感知系统，那么在向右运动适应后，仍然应该观察到一个单一的心理测量函数。然而，如果向左和向右探测器独立运作，那么函数的左半部分和右半部分的斜率可能不同，特别是在单向适应之后。我们测量了5名观察者在有和没有先前向右运动适应的情况下，对于9个运动一致性值的“向右”方向反应的概率。虽然在没有运动适应的情况下发现了一个平滑的心理测量函数，但在适应后，心理测量函数的右半部分变平，而左半部分保持不变。这些结果表明，运动方向分析器以非拮抗的方式运作。
