Ledgeway T
Department of Psychology, University of London, Royal Holloway College, Egham, Surrey, U.K.
Vision Res. 1996 Aug;36(16):2489-95. doi: 10.1016/0042-6989(95)00315-0.
Direction-discrimination performance was measured for two-frame random-dot kinematograms in which one or both frames were spatial frequency filtered with a one octave band-pass filter and the centre frequency of this filter was varied in the range 0.75-9 c/deg independently for each frame. When both frames were filtered so that they contained common (overlapping) spatial frequencies direction discrimination was extremely good but it deteriorated rapidly as the degree of spectral overlap between the two frames decreased. These results are consistent with previous findings that suggest that the mechanisms that mediate the initial stages of motion detection are narrowly tuned for spatial frequency and cannot combine information conveyed at disparate frequencies in order to compute an unambiguous estimate of the direction of local motion. However, when only one of the frames was band-pass filtered and the other was unfiltered (broadband), the correct direction of stimulus motion could be discriminated reliably for a broad range of filter centre frequencies. Performance was best when the centre frequency of the filtered frame was at medium spatial frequencies and tended to deteriorate as the centre frequency approached either extreme of the spatial frequency range examined. This basic pattern of results may be attributed to the visual system's differential sensitivity to the Fourier components present in the unfiltered frame.
针对双帧随机点运动图测量了方向辨别性能，其中一帧或两帧都用一个倍频程带通滤波器进行空间频率滤波，并且该滤波器的中心频率在0.75 - 9周/度范围内对每一帧独立变化。当两帧都经过滤波从而包含共同（重叠）的空间频率时，方向辨别非常好，但随着两帧之间频谱重叠程度降低，辨别能力迅速下降。这些结果与先前的研究结果一致，先前研究表明介导运动检测初始阶段的机制对空间频率进行了窄调谐，并且不能组合以不同频率传递的信息来计算局部运动方向的明确估计。然而，当只有一帧进行带通滤波而另一帧未滤波（宽带）时，在很宽的滤波器中心频率范围内都能可靠地辨别刺激运动的正确方向。当滤波帧的中心频率处于中等空间频率时性能最佳，并且随着中心频率接近所研究空间频率范围的任一极端，性能往往会下降。这种基本的结果模式可能归因于视觉系统对未滤波帧中存在的傅里叶分量的差异敏感性。
