DIFFERENT PROCESSES UNDERLIE THE DETECTION OF 2ND-ORDER MOTION AT LOW AND HIGH TEMPORAL FREQUENCIES
DIFFERENT PROCESSES UNDERLIE THE DETECTION OF 2ND-ORDER MOTION AT LOW AND HIGH TEMPORAL FREQUENCIES
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DOI：
10.1098/rspb.1994.0111
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发表时间：
1994-08-22
影响因子：
4.7
通讯作者：
ANDERSON, SJ
中科院分区：
文献类型：
--
作者：
HOLLIDAY, IE;ANDERSON, SJ
该项目的目的是确定一阶和二阶运动刺激是否由相同的机制检测到。我们首先测量用于 0.3 c deg(-1) 漂移空间拍模式和亮度调制光栅的方向辨别的时间对比敏感度函数 (CSF)。心跳模式的 CSF 是双峰的，灵敏度在 1-2 Hz 和 10-12 Hz 附近最大。相比之下，亮度光栅的 CSF 在 10 Hz 附近有一个单峰。然后使用节拍模式和亮度光栅的所有排列作为测试和适应刺激来完成单独的适应实验。一般来说，在适应时间频率在大范围内变化的模式之前和之后测量对固定时间频率（2、4、8或16Hz）的测试模式的敏感性。这些实验的基本原理是，如果一阶和二阶刺激由相同的机制处理，则适应调谐曲线应该都是相似的。我们的结果表明，在高时间频率（> 4 Hz）时是这种情况，但在低时间频率时则不然。时间频率为 8 Hz 和 16 Hz 的测试模式的适应后灵敏度函数是带通的，在 12 Hz 附近具有最大适应，并且显示了节拍特异性适应的证据；对于 2 Hz 测试模式，灵敏度函数为低通，适应性在 20 Hz 以上下降，但没有节拍特定的适应性。 CSFS 的形状和适应实验的结果表明，单独的过程介导了低和高时间频率下漂移节拍模式的检测。结果与以下假设一致：快速二阶运动是通过傅里叶型机制检测到的，之前是非线性，而慢速二阶运动是通过涉及局部亮度特征比较的过程来检测的。
The aim of this project was to determine whether first- and second-order motion stimuli are detected by the same mechanism. We began by measuring the temporal contrast sensitivity function (CSF) for the directional discrimination of 0.3 c deg(-1) drifting spatial beat patterns and luminance modulated gratings. The CSF for beat patterns was bimodal, with sensitivity maximal near 1-2 Hz and 10-12 Hz. In contrast, the CSF for luminance gratings had a single peak near 10 Hz. Separate adaptation experiments were then done using all permutations of beat patterns and luminance gratings as the test and adaptation stimuli. In general, sensitivity to a test pattern of fixed temporal frequency (2, 4, 8 or 16 Hz) was measured both before and after adaptation to patterns whose temporal frequency varied over a wide range. The rationale for these experiments was that if first- and second-order stimuli are processed by the same mechanisms, the adaptation tuning curves should all be similar. Our results show that this is the case at high temporal frequencies (> 4 Hz), but not at low temporal frequencies. The post-adaptation sensitivity functions for test patterns with temporal frequencies of 8 Hz and 16 Hz were bandpass, with maximal adaptation near 12 Hz, and showed evidence of beat-specific adaptation; for 2 Hz test patterns the sensitivity functions were lowpass, adaptation declining above 20 Hz, but there was no beat-specific adaptation. The shape of the CSFS and the results of the adaptation experiments show that separate processes mediate the detection of drifting beat patterns at low and high temporal frequencies. The results are consistent with the hypothesis that fast second-order motion is detected by Fourier-type mechanisms, preceded by a nonlinearity, and slow second-order motion is detected by a process involving a comparison of local luminance features.