Undergraduate Neuroscience Program, Krieger School of Arts & Sciences, Johns Hopkins University, Baltimore, MD.
Section on Light and Circadian Rhythms, National Institute of Mental Health, National Institutes of Health, Bethesda, MD.
J Biol Rhythms. 2017 Dec;32(6):621-626. doi: 10.1177/0748730417736960. Epub 2017 Nov 12.
Artificial light in modern society has led to the ubiquity of light exposure at night as individuals work night shifts and use light-emitting electronic devices before bedtime. These aberrant light conditions have detrimental consequences on cognitive and mental health, compelling the need to understand the mechanisms by which light affects brain functions. Although it was believed that aberrant light impairs health by first disrupting circadian rhythms and sleep, we showed that chronic exposure to a light cycle termed T7 (3.5 h of darkness, 3.5 h of light) caused mood and learning dysfunction in adult mice independent of sleep deprivation or circadian arrhythmicity, suggesting the direct effects of aberrant light on brain function. However, the mechanisms by which light directly causes mood and learning dysfunction remain poorly understood. In this study, we sought to determine whether exposure to the T7 cycle disrupts adult hippocampal neurogenesis, given that suppressed neurogenesis has been correlated with mood and learning dysfunction. After exposing adult mice to the T7 light cycle, we analyzed adult hippocampal neurogenesis by examining cellular proliferation and number of adult-born neurons. Contrary to our hypothesis that T7 would suppress neurogenesis, we found that adult mice exposed to 2 or 10 weeks of the T7 light cycle did not exhibit deficits in hippocampal neurogenesis. Our findings suggest that the direct effects of light on mood and learning do not depend on adult hippocampal neurogenesis.
在现代社会中，由于个体上夜班和在睡前使用发光电子设备，夜间光照暴露变得无处不在。这些异常的光照条件对认知和心理健康产生了有害影响，因此需要了解光照影响大脑功能的机制。尽管人们认为异常的光照首先通过打乱昼夜节律和睡眠来损害健康，但我们表明，慢性暴露于一种称为 T7 的光照周期（3.5 小时黑暗，3.5 小时光照）会导致成年小鼠出现情绪和学习功能障碍，而与睡眠剥夺或昼夜节律失常无关，这表明异常光照对大脑功能有直接影响。然而，光照直接导致情绪和学习功能障碍的机制仍知之甚少。在这项研究中，我们试图确定暴露于 T7 周期是否会破坏成年海马神经发生，因为抑制神经发生与情绪和学习功能障碍有关。在将成年小鼠暴露于 T7 光照周期后，我们通过检查细胞增殖和成年神经元数量来分析成年海马神经发生。与我们的假设相反，即 T7 会抑制神经发生，我们发现暴露于 T7 光照周期 2 或 10 周的成年小鼠并未表现出海马神经发生缺陷。我们的研究结果表明，光照对情绪和学习的直接影响不依赖于成年海马神经发生。
