Intrinsically photosensitive retinal ganglion cells convey intrinsic, melanopsin‐based, photoreceptive signals alongside those produced by rods and cones to the suprachiasmatic nucleus (SCN) circadian clock. To date, experimental data suggest that melanopsin plays a more significant role in measuring ambient light intensity than cone photoreception. Such studies have overwhelmingly used diffuse light stimuli, whereas light intensity in the world around us varies across space and time. Here, we investigated the extent to which melanopsin or cone signals support circadian irradiance measurements in the presence of naturalistic spatiotemporal variations in light intensity. To address this, we first presented high‐ and low‐contrast movies to anaesthetised mice whilst recording extracellular electrophysiological activity from the SCN. Using a mouse line with altered cone sensitivity (Opn1mw^R mice) and multispectral light sources we then selectively varied irradiance of the movies for specific photoreceptor classes. We found that steps in melanopic irradiance largely account for the light induced‐changes in SCN activity over a range of starting light intensities and in the presence of spatiotemporal modulation. By contrast, cone‐directed changes in irradiance only influenced SCN activity when spatiotemporal contrast was low. Consistent with these findings, under housing conditions where we could independently adjust irradiance for melanopsin versus cones, the period lengthening effects of constant light on circadian rhythms in behaviour were reliably determined by melanopic irradiance, regardless of irradiance for cones. These data add to the growing evidence that modulating effective irradiance for melanopsin is an effective strategy for controlling the circadian impact of light.

中文翻译：

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针对黑视蛋白的辐照度调节，而不是视锥光感受器，可靠地改变了视交叉上核的电生理活动和小鼠的昼夜节律行为

内在光敏视网膜神经节细胞将内在的、基于黑视蛋白的光感受信号与视杆细胞和视锥细胞产生的信号一起传送到视交叉上核 (SCN) 生物钟。迄今为止，实验数据表明黑视蛋白在测量环境光强度方面比锥体光感受作用更重要。此类研究绝大多数使用漫射光刺激，而我们周围世界的光强度随空间和时间而变化。在这里，我们研究了在存在光强度的自然时空变化的情况下，黑视蛋白或视锥细胞信号支持昼夜节律辐照度测量的程度。为了解决这个问题，我们首先向麻醉的小鼠展示了高对比度和低对比度的电影，同时记录了来自 SCN 的细胞外电生理活动。Opn1mw ^R小鼠）和多光谱光源，然后我们有选择地改变特定感光器类别的电影辐照度。我们发现黑色素辐照度的步骤在很大程度上解释了在一系列起始光强度和时空调制的情况下 SCN 活动的光诱导变化。相比之下，当时空对比度较低时，辐照度的锥形变化仅影响 SCN 活动。与这些发现一致，在我们可以独立调整黑视蛋白与视锥细胞的辐照度的住房条件下，恒定光对行为昼夜节律的周期延长效应由黑视素辐照度可靠地确定，而不管视锥细胞的辐照度如何。