Investigation of the-visual processes mediating the pupillary light responses

为了建立一种非侵入性的、客观的用于人类视觉处理的探测器，本研究探讨了调节由颜色变化引起的瞳孔反应的视觉机制。目前的调查结果可以总结如下。(1)彩色瞳孔反应的特性在几个方面与知觉反应的特性相似(即，检测阈值)。这两种反应都是由锥体相反信号驱动的，至少部分是由(L-M)染色过程介导的。在(L-M)过程中，视锥-对手相互作用是减法的，L-视锥信号的权重与M-视锥信号的权重几乎相同。(2)瞳孔反应的时间反应特性部分类似于参与颜色检测的视网膜神经节细胞(PC细胞)的反应特性，因为彩色的瞳孔反应呈现出持续的(和瞬时的)反应波形。(3)通过颜色对比度适应可以类似于知觉反应来降低瞳孔反应的敏感度。这一发现表明，大脑皮层的染色过程对瞳孔反应有贡献。这些结果加深了对瞳孔视觉过程的功能特性的理解，并提示驱动瞳孔反应的视觉信号来自视网膜中的PC细胞，通过一些皮质区域，视觉信号将在那里进行实质性的转换。此外，目前的研究结果表明，瞳孔测量法可以用来研究不同对比度水平的颜色反应，范围从接近阈值到至少高于阈值2个对数单位。综上所述，本研究提供了聚合证据，表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的探针。

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.