Vision Science Program, University of California, Berkeley, California 94720; and Graduate Program in Bioengineering, University of California, Berkeley, California 94720 and University of California, San Francisco, California 94143.
J Neurosci. 2014 Jan 22;34(4):1397-408. doi: 10.1523/JNEUROSCI.1652-13.2014.
To encode binocular disparity, the visual system determines the image patches in one eye that yield the highest correlation with patches in the other eye. The computation of interocular correlation occurs after spatiotemporal filtering of monocular signals, which leads to restrictions on disparity variations that can support depth perception. We quantified those restrictions by measuring humans' ability to see disparity variation at a wide range of spatial and temporal frequencies. Lower-disparity thresholds cut off at very low spatiotemporal frequencies, which is consistent with the behavior of V1 neurons. Those thresholds are space-time separable, suggesting that the underlying neural mechanisms are separable. We also found that upper-disparity limits were characterized by a spatiotemporal, disparity-gradient limit; to be visible, disparity variation cannot exceed a fixed amount for a given interval in space-time. Our results illustrate that the disparity variations that humans can see are very restricted compared with the corresponding luminance variations. The results also provide insight into the neural mechanisms underlying depth from disparity, such as why stimuli with long interocular delays can still yield clear depth percepts.
为了对双目视差进行编码，视觉系统会确定一只眼中与另一只眼中的视差匹配程度最高的图像块。双眼相关的计算发生在对单眼信号进行时空滤波之后，这会对视差变化造成限制，从而影响深度感知。我们通过测量人类在各种空间和时间频率下感知视差变化的能力，量化了这些限制。较低视差的阈值在非常低的时空频率下截止，这与 V1 神经元的行为一致。这些阈值在时空上是可分离的，表明潜在的神经机制是可分离的。我们还发现，较高视差的限制由时空、视差梯度限制决定；为了可见，视差变化在给定的时空间隔内不能超过固定量。我们的研究结果表明，与相应的亮度变化相比，人类能够看到的视差变化受到了非常大的限制。这些结果也为基于视差的深度感知的神经机制提供了一些见解，例如为什么具有长眼间延迟的刺激仍然可以产生清晰的深度感知。
