Temporal integration of optic flow, measured by contrast and coherence thresholds
Temporal integration of optic flow, measured by contrast and coherence thresholds
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DOI：
10.1016/s0042-6989(01)00072-4
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发表时间：
2001-07-01
期刊：
影响因子：
1.8
通讯作者：
Santoro, L
中科院分区：
文献类型：
--
作者：
Burr, DC;Santoro, L
我们测量，作为曝光持续时间的函数，对比灵敏度和相干灵敏度辨别随机点图案在圆形，径向或平移方向上移动的运动方向。这些模式的对比敏感度随曝光持续时间线性增加，最多约200-300 ms，与早期运动单元的时间总和的先前估计一致。然而，相干灵敏度显示出更长的求和周期，约3秒。当刺激嵌入在10 s的噪声内时，灵敏度随着持续时间增加到2-3 s，近似线性地，如理想积分器所预期的那样。当没有噪声周期时，灵敏度也增加了，但方式不同。对于径向和圆周运动，在与嵌入噪声相同的持续时间内（约3 s），增加趋向于理论预测的平方根关系。然而，对于翻译，曲线是陡峭的理论预测（近线性），和求和估计约1000毫秒。当目标的持续时间是恒定的在200毫秒，但侧翼噪声变化，灵敏度下降，总持续时间在一个类似的时间间隔。我们解释我们的结果以反映至少两个阶段的分析，具有200-300 ms的时间常数的局部运动分析的阈值限制的早期阶段，以及具有长得多的时间常数的稍后的全局运动整合阶段，大约3000 ms。积分时间约为1000 ms。（C）2001 Elsevier Science Ltd.保留所有权利。
We measured, as a function of exposure duration, contrast sensitivity and coherence sensitivity for discerning the direction of motion of random dot patterns moving in circular, radial or translational directions. Contrast sensitivity for these patterns increased linearly with exposure duration, up to about 200-300 ms, consistent with previous estimates of temporal summation of early motion units. Coherence sensitivity, however, showed much longer summation periods, about 3 s. When the stimulus was embedded within 10 s of noise, sensitivity increased with duration up to 2-3 s, approximately linearly, as expected from an ideal integrator. When presented without the noise period, sensitivity also increased, but in a different way. For radial and circular motion the increase tended towards the theoretically predicted square root relationship for the same duration as that found with the embedded noise (about 3 s). For translation, however, the curve was steeper than the theoretical prediction (nearly linear), and the summation estimates of around 1000 ms. When the duration of the target was constant at 200 ms, but that of the flanking noise varied, sensitivity decreased with total duration over a similar interval. We interpret our results to reflect at least two stages of analysis, a threshold-limited early stage of local-motion analysis, with a time constant of 200-300 ms, and a later global-motion integration stage with a much longer time constant, around 3000 ms. There may also exist an intermediate stage, with an integration time of around 1000 ms. (C) 2001 Elsevier Science Ltd. All rights reserved.