What is noise for the motion system?
What is noise for the motion system?
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DOI：
10.1016/0042-6989(95)00325-8
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发表时间：
1996-08-01
期刊：
影响因子：
1.8
通讯作者：
Raymond, JE
中科院分区：
文献类型：
--
作者：
Scase, MO;Braddick, OJ;Raymond, JE
随机点模式的运动相干阈值已被广泛采用作为视觉运动处理性能的衡量标准，然而，在必须检测相干运动信号的“噪声”类型中存在多样性。在这里，我们比较了三种产生运动噪声的方法的相干阈值：在每个新帧中在随机位置重新绘制点；具有固定位移但从一帧到另一帧随机游走的点；或在任意方向上移动的点，对于给定的点在一系列位移中保持不变。在每种情况下，信号点可以在整个显示序列中保持相同，或者可以在每一帧上重新选择信号点（“不同”）。在我们的显示（3度正方形，120毫秒曝光，速度= 5或10度秒（-1））中，所有这些不同的噪声条件产生了相似的阈值，约为5-8%，条件之间存在一些小但系统的差异。随机方向显示的阈值始终高于随机行走或随机位置显示的阈值，特别是在较低的速度下。然而，这种影响远小于随机方向上噪声平均值标准误差的增加所期望的，这可能是因为运动系统在局部空间和/或时间区域内最有效地集成了信息。随机行走阈值和随机位置阈值之间的相似性表明，在后一种情况下，受试者不会利用信号点和噪声点之间速度分布的显著差异来解释受试者的表现。使用相干阈值设计和解释实验的实际信息是，至少在这里测试的刺激范围内，噪声的选择对结果的影响不大。版权所有爱思唯尔科学有限公司
Motion coherence thresholds in random-dot patterns have been widely adopted as a measure of performance in visual motion processing, However, there has been diversity in the type of ''noise'' in which a coherent motion signal has to be detected. Here we compare coherence thresholds for three ways of creating motion noise: dots replotted in random positions in each new frame; dots with a set displacement but following a random walk from frame to frame; or dots moving in random directions which remain constant for a given dot over a sequence of displacements. In each case, the signal dots may either remain the same throughout the display sequence, or the signal dots may be re-selected afresh on each frame (''different'').With our display (3 deg square, 120 msec exposure, velocity = 5 or 10 deg sec(-1)), all these different noise conditions yielded similar thresholds around 5-8%, There were some small but systematic differences between conditions. Thresholds in random-direction displays were consistently higher than those in random-walk or random-position displays, especially at the lower velocity, However, this effect is much smaller than would be expected from the increased standard error of the noise mean in random direction, perhaps because the motion system integrates information most effectively over a local region of space and/or time. Subjects'' performance could not be explained by a strategy of identifying individual signal dots with extended trajectories, The similarity between random-walk and random-position thresholds implies that subjects do not exploit the marked differences in speed distribution between signal and noise dots in the latter case.The practical message for the design and interpretation of experiments using coherence thresholds is that the results are not much affected by the choice of noise, at least within the range of stimuli tested here. Copyright (C) 1996 Elsevier Science Ltd.