Yang Y, Blake R
Department of Psychology, Vanderbilt University, Nashville, TN 37240.
Vision Res. 1991;31(7-8):1177-89. doi: 10.1016/0042-6989(91)90043-5.
A masking paradigm was employed to measure the spatial frequency selectivity of channels underlying human stereopsis. Observers viewed spatially filtered (0.4 octave bandwidth) random-dot stereograms in which a disparate bar appeared in either the top or bottom half of the display; superimposed on one RDS half-image was a noise target whose spatial frequency content was varied relative to that of the RDS. A staircase procedure was used to measure the monocular noise energy (and hence the signal-to-noise ratio) at which observers could judge the location of the disparate bar on 71% of trials. Statistical analyses showed that the resulting stereoscopic masking functions could be grouped into two sets, one with peak sensitivity at 3 c/deg and the other with peak sensitivity at 5 c/deg. These two channels were observed for both crossed and uncrossed disparities ranging from coarse to fine. Essentially the same results were obtained with binocular noise and with stereo displays flashed too briefly to be affected by eye movements. Our results are inconsistent with models of stereopsis in which the disparity range to which a channel is sensitive varies with that channel's peak spatial frequency. These data imply that the spatial frequency selectivity of stereopsis differs from the tuning of spatial channels underlying the detection and discrimination of form.
采用一种掩蔽范式来测量人类立体视觉所基于的通道的空间频率选择性。观察者观看空间滤波（0.4倍频程带宽）的随机点立体图，其中一个视差条出现在显示屏的上半部分或下半部分；叠加在一个随机点立体图半图像上的是一个噪声目标，其空间频率内容相对于随机点立体图而变化。使用阶梯法来测量单眼噪声能量（从而测量信噪比），在该信噪比下观察者能够在71%的试验中判断视差条的位置。统计分析表明，所得到的立体掩蔽函数可分为两组，一组在3周/度处具有峰值敏感性，另一组在5周/度处具有峰值敏感性。对于从粗到细的交叉和非交叉视差，都观察到了这两个通道。使用双眼噪声以及闪烁时间过短以至于不受眼球运动影响的立体显示时，基本上得到了相同的结果。我们的结果与立体视觉模型不一致，在这些模型中，通道敏感的视差范围随该通道的峰值空间频率而变化。这些数据表明，立体视觉的空间频率选择性不同于基于形状检测和辨别所涉及的空间通道的调谐。
