Light is the most effective environmental stimulus for shifting the mammalian circadian pacemaker. Numerous studies have been conducted across multiple species to delineate wavelength, intensity, duration, and timing contributions to the response of the circadian pacemaker to light. Recent studies have revealed a surprising sensitivity of the human circadian pacemaker to short pulses of light. Such responses have challenged photon counting-based theories of the temporal dynamics of the mammalian circadian system to both short- and long-duration light stimuli. Here, we collate published light exposure data from multiple species, including gerbil, hamster, mouse, and human, to investigate these temporal dynamics and explore how the circadian system integrates light information at both short- and long-duration time scales to produce phase shifts. Based on our investigation of these data sets, we propose 3 new interpretations: (1) intensity and duration are independent factors of total phase shift magnitude, (2) the possibility of a linear/log temporal function of light duration that is universal for all intensities for durations less than approximately 12 min, and (3) a potential universal minimum light duration of ~0.7 sec that describes a "dead zone" of light stimulus. We show that these properties appear to be consistent across mammalian species. These interpretations, if confirmed by further experiments, have important practical implications in terms of understanding the underlying physiology and for the design of lighting regimens to reset the mammalian circadian pacemaker.

中文翻译：

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对短期和长期光照的昼夜节律重置反应的时间动态的探索：跨物种一致性和差异。

光是改变哺乳动物昼夜节律起搏器的最有效的环境刺激。已经在多个物种中进行了大量研究，以描述波长、强度、持续时间和时间对昼夜节律起搏器对光的反应的影响。最近的研究揭示了人类昼夜节律起搏器对短光脉冲的惊人敏感性。这种反应对基于光子计数的哺乳动物昼夜节律系统对短期和长期光刺激的时间动力学理论提出了挑战。在这里，我们整理了来自多个物种（包括沙鼠、仓鼠、小鼠和人类）的已发表的光暴露数据，以研究这些时间动态并探索昼夜节律系统如何在短期和长期时间尺度上整合光信息以产生相移。基于我们对这些数据集的调查，我们提出了 3 种新的解释：(1) 强度和持续时间是总相移幅度的独立因素，(2) 光持续时间的线性/对数时间函数对所有情况通用的可能性持续时间小于约 12 分钟的强度，以及 (3) 潜在的通用最小光持续时间约为 0.7 秒，描述了光刺激的“死区”。我们证明这些特性在哺乳动物物种中似乎是一致的。这些解释如果通过进一步的实验得到证实，对于理解潜在的生理学和设计重置哺乳动物昼夜节律起搏器的照明方案具有重要的实际意义。