Investigation of the-visual processes mediating the pupillary light responses

为了使瞳孔测量技术成为一种无创、客观的人类视觉加工探针，本研究探讨了颜色变化诱发瞳孔反应的视觉机制。目前的研究结果可以总结如下。(1)彩色瞳孔反应的性质在几个方面与知觉反应（即检测阈值）相似。这两种反应都是由锥体对抗信号驱动的，至少部分是由（L-M）色过程介导的。在（L-M）过程中，锥-对手相互作用是相减的，并且l -锥信号的权值与m -锥信号的权值几乎相同。(2)瞳孔反应的时间响应特性部分类似于介导颜色检测的视网膜神经节细胞（PC细胞），彩色瞳孔反应表现出持续（以及短暂）的响应波形。(3)瞳孔反应的敏感性可以通过颜色对比适应类似于知觉反应的方式降低。这一发现表明，皮层染色过程有助于瞳孔反应。这些结果提高了对瞳孔视觉过程的功能特性的理解，并表明驱动瞳孔反应的视觉信号来自视网膜的PC细胞，通过一些皮质区域，视觉信号将发生实质性的转换。此外，目前的结果表明，瞳孔测量法可用于研究从接近阈值到至少高于阈值2个对数单位的各种对比度水平下的色度响应。综上所述，本研究提供了越来越多的证据，证明瞳孔测量法可以作为一种有用的、有前途的人类视觉处理探针。

To establish the pupillometry as a noninvasive and objective probe for visual processing in humans, the present study investigated the visual mechanism mediating the pupillary response evoked by chromatic changes. The present findings can be summarized as follows. (1) The properties of the chromatic pupillary response are similar in several aspects to those of the perceptual responses (I.e., detection thresholds). Both responses are driven by cone-opponent signals and at least partially mediated by an (L-M) chromatic process. The cone-opponent interaction in the (L-M) process is subtractive and the weight for L-cone signals is almost identical to that for M-cone signals. (2) The temporal response properties of the pupillary response are partially similar to those of the retinal ganglion cells (PC cells) mediating color detection in that the chromatic pupillary response exhibits a sustained (as well as transient) response wave form. (3) The sensitivity of the pupillary response can be reduced in a similar way to the perceptual response by color-contrast adaptation. This finding suggests that cortical chromatic processes contribute to the pupillary response. These results improve the understanding of the functional properties of the pupillary visual process and suggest that the visual signals driving the pupillary response come from PC cells in the retina via some cortical areas where the visual signals would be transformed substantially. In addition, the present results showed that the pupillometry can be used to investigate, chromatic responses at various contrast levels ranging from near-threshold to at least 2 log units above threshold.In summary, the present study provided converging evidence that the pupillometry can be a useful and promising probe for visual processing in humans.