Gegenfurtner K R, Hawken M J
Center for Neural Science, New York University, NY 10003, USA.
Vision Res. 1996 May;36(9):1281-90. doi: 10.1016/0042-6989(95)00198-0.
We measured perceived velocity as a function of contrast for luminance and isoluminant sinusoidal gratings, luminance and isoluminant plaids, and second-order, amplitude-modulated, drift-balanced stimuli. For all types of stimuli perceived velocity was contrast-invariant for fast moving patterns at or above 4 deg/sec. For slowly moving stimuli the log of perceived velocity was a linear function of the log of the contrast. The slope of this perceived velocity-vs-contrast line (velocity gain) was relatively shallow for luminance gratings and luminance plaids, but was steep for isoluminant gratings and isoluminant plaids, as well as for drift-balanced stimuli. Independent variation of spatial and temporal frequency showed that these variables, and not velocity alone, determine the velocity gain. Overall, the results indicate that slow moving stimuli defined by chromaticity or by second-order statistics are processed in a different manner from luminance defined stimuli. We propose that there are a number of independent mechanisms processing motion targets and it is the interplay of these mechanisms that is responsible for the final percept.
亮度和等亮度正弦光栅、亮度和等亮度方格图案，以及二阶、幅度调制、漂移平衡刺激。对于所有类型的刺激，在速度为4度/秒及以上的快速移动图案中，感知速度与对比度无关。对于缓慢移动的刺激，感知速度的对数是对比度对数的线性函数。对于亮度光栅和亮度方格图案，这种感知速度与对比度线（速度增益）的斜率相对较浅，但对于等亮度光栅和等亮度方格图案以及漂移平衡刺激，斜率则较陡。空间和时间频率的独立变化表明，这些变量而非仅速度决定了速度增益。总体而言，结果表明由色度或二阶统计定义的缓慢移动刺激与由亮度定义的刺激处理方式不同。我们提出存在多种独立机制处理运动目标，正是这些机制的相互作用导致了最终的感知。
