J Opt Soc Am A Opt Image Sci Vis. 2020 Apr 1;37(4):A81-A88. doi: 10.1364/JOSAA.382349.
A large number of studies have shown the effect of melanopsin-dependent retinal ganglion cells on humans performing brightness discrimination tasks. These studies often utilized targets that only differ in their melanopsin activation levels, and not in their luminance or hue, which are both factors that make large contributions to brightness discrimination. The purpose of the present study was to evaluate the relative contribution of melanopsin activation to brightness discrimination when luminance and hue are also varying in addition to melanopsin activation. Using an apparatus consisting of three separate high luminance projectors, we were able to manipulate melanopsin-isolating stimulation, and L-, M-, and S-cone stimulation separately, thus allowing us to vary stimuli in their melanopsin activation, luminance, and hue category independently. We constructed three sets of target stimuli with three different levels of melanopsin activation (100%, 131%, and 167% relative melanopsin excitation) and five levels of luminance. We then had subjects do a two-alternative forced choice task where they compared the previously described target stimuli set to a set of four comparison stimuli that varied in their hue category but had identical luminances. We found that in our stimuli set the overall contribution of melanopsin activity to brightness discrimination was small (an average of 6% increase in likelihood to call a high melanopsin activity stimulus brighter compared to a low melanopsin activity stimulus) when luminance and hue also varied. However, a significant interaction showed that when the comparison was between stimuli differing only in melanopsin stimulation (with luminance and hue unchanged) the contribution of melanopsin to brightness judgments was about 3 times larger (an average of 18% increase in likelihood to call a high melanopsin activity stimulus brighter compared to a low melanopsin activity stimulus). This suggests that although luminance and hue have large effects on brightness discrimination such that the melanopsin contribution can become hard to detect, when there are minimal cone-dependent signals available, melanopsin can make a large contribution to brightness discrimination.
大量研究表明，依赖黑视蛋白的视网膜神经节细胞对人类进行亮度辨别任务有影响。这些研究通常使用的目标物仅在黑视蛋白激活水平上有所不同，而在亮度和色调上则没有差异，因为这些因素对亮度辨别有很大的贡献。本研究的目的是评估在亮度和色调也在变化的情况下，除了黑视蛋白激活之外，黑视蛋白激活对亮度辨别的相对贡献。我们使用由三个单独的高亮度投影仪组成的装置，能够分别操纵黑视蛋白隔离刺激、L、M 和 S 锥体刺激，从而使我们能够独立地改变刺激物的黑视蛋白激活、亮度和色调类别。我们构建了三组目标刺激物，每组刺激物的黑视蛋白激活水平（相对黑视蛋白激发的 100%、131%和 167%）和五个亮度水平不同。然后，我们让受试者进行二选一的强制选择任务，他们将之前描述的目标刺激物集与一组四个比较刺激物进行比较，这些比较刺激物在色调类别上有所不同，但亮度相同。我们发现，在我们的刺激物集中，当亮度和色调也发生变化时，黑视蛋白活动对亮度辨别的总体贡献很小（与低黑视蛋白活动刺激相比，高黑视蛋白活动刺激更亮的可能性平均增加 6%）。然而，显著的相互作用表明，当比较的是仅在黑视蛋白刺激上有所不同的刺激物（亮度和色调不变）时，黑视蛋白对亮度判断的贡献大约大三倍（与低黑视蛋白活动刺激相比，高黑视蛋白活动刺激更亮的可能性平均增加 18%）。这表明，尽管亮度和色调对亮度辨别有很大的影响，以至于黑视蛋白的贡献难以察觉，但当可用的锥体细胞信号最小化时，黑视蛋白可以对亮度辨别做出很大的贡献。
