Storchi Riccardo, Milosavljevic Nina, Eleftheriou Cyril G, Martial Franck P, Orlowska-Feuer Patrycja, Bedford Robert A, Brown Timothy M, Montemurro Marcelo A, Petersen Rasmus S, Lucas Robert J
Faculty of Life Sciences, University of Manchester, M13 9PT Manchester, United Kingdom;
Department of Neurophysiology and Chronobiology, Institute of Zoology, Jagiellonian University, 30-387 Krakow, Poland.
Proc Natl Acad Sci U S A. 2015 Oct 20;112(42):E5734-43. doi: 10.1073/pnas.1505274112. Epub 2015 Oct 5.
Twice a day, at dawn and dusk, we experience gradual but very high amplitude changes in background light intensity (irradiance). Although we perceive the associated change in environmental brightness, the representation of such very slow alterations in irradiance by the early visual system has been little studied. Here, we addressed this deficit by recording electrophysiological activity in the mouse dorsal lateral geniculate nucleus under exposure to a simulated dawn. As irradiance increased we found a widespread enhancement in baseline firing that extended to units with ON as well as OFF responses to fast luminance increments. This change in baseline firing was equally apparent when the slow irradiance ramp appeared alone or when a variety of higher-frequency artificial or natural visual stimuli were superimposed upon it. Using a combination of conventional knockout, chemogenetic, and receptor-silent substitution manipulations, we continued to show that, over higher irradiances, this increase in firing originates with inner-retinal melanopsin photoreception. At the single-unit level, irradiance-dependent increases in baseline firing were strongly correlated with improvements in the amplitude of responses to higher-frequency visual stimuli. This in turn results in an up to threefold increase in single-trial reliability of fast visual responses. In this way, our data indicate that melanopsin drives a generalized increase in dorsal lateral geniculate nucleus excitability as dawn progresses that both conveys information about changing background light intensity and increases the signal:noise for fast visual responses.
每天黎明和黄昏时分，我们会经历背景光强度（辐照度）逐渐但幅度很大的变化。尽管我们能感知到环境亮度的相关变化，但早期视觉系统对这种非常缓慢的辐照度变化的表征却很少被研究。在这里，我们通过记录小鼠背侧外侧膝状核在模拟黎明光照下的电生理活动来解决这一不足。随着辐照度增加，我们发现基线放电广泛增强，这种增强扩展到了对快速亮度增加有开反应和关反应的神经元。当缓慢的辐照度斜坡单独出现或叠加各种高频人工或自然视觉刺激时，基线放电的这种变化同样明显。通过结合传统基因敲除、化学遗传学和受体沉默替代操作，我们进一步表明，在更高的辐照度下，这种放电增加源于视网膜内的黑视蛋白光感受器。在单神经元水平上，基线放电的辐照度依赖性增加与对高频视觉刺激反应幅度的改善密切相关。这进而导致快速视觉反应的单次试验可靠性提高了两倍。通过这种方式，我们的数据表明，随着黎明的推进，黑视蛋白驱动背侧外侧膝状核兴奋性普遍增加，这既传达了背景光强度变化的信息，又增加了快速视觉反应的信号噪声比。
