Department of Neurobiology, Duke University School of Medicine , Durham, North Carolina.
Systems Neurobiology Laboratories, Salk Institute for Biological Studies , La Jolla, California.
J Neurophysiol. 2019 Jan 1;121(1):255-268. doi: 10.1152/jn.00683.2018. Epub 2018 Nov 28.
Sensory receptor noise corrupts sensory signals, contributing to imperfect perception and dictating central processing strategies. For example, noise in rod phototransduction limits our ability to detect light, and minimizing the impact of this noise requires precisely tuned nonlinear processing by the retina. But detection sensitivity is only one aspect of night vision: prompt and accurate behavior also requires that rods reliably encode the timing of photon arrivals. We show here that the temporal resolution of responses of primate rods is much finer than the duration of the light response and identify the key limiting sources of transduction noise. We also find that the thermal activation rate of rhodopsin is lower than previous estimates, implying that other noise sources are more important than previously appreciated. A model of rod single-photon responses reveals that the limiting noise relevant for behavior depends critically on how rod signals are pooled by downstream neurons. NEW & NOTEWORTHY Many studies have focused on the visual system's ability to detect photons, but not on its ability to encode the relative timing of detected photons. Timing is essential for computations such as determining the velocity of moving objects. Here we examine the timing precision of primate rod photoreceptor responses and show that it is more precise than previously appreciated. This motivates an evaluation of whether scotopic vision approaches limits imposed by rod temporal resolution.
感觉受体噪声会干扰感觉信号，导致感知不完美，并决定中枢处理策略。例如，杆状光传导中的噪声限制了我们检测光的能力，而最小化这种噪声的影响需要视网膜进行精确调谐的非线性处理。但检测灵敏度只是夜视的一个方面：快速准确的行为还需要 rods 可靠地编码光子到达的时间。我们在这里表明，灵长类动物 rods 的反应时间分辨率比光响应的持续时间精细得多，并确定了转导噪声的关键限制源。我们还发现视蛋白的热激活率低于之前的估计，这意味着其他噪声源比以前认为的更为重要。rod 单光子响应模型表明，与行为相关的限制噪声在很大程度上取决于下游神经元如何汇集 rod 信号。新的和值得注意的是，许多研究都集中在视觉系统检测光子的能力上，但没有研究其检测到的光子相对时间的编码能力。时间对于诸如确定移动物体的速度等计算至关重要。在这里，我们检查了灵长类动物 rod 光感受器反应的时间精度，并表明它比以前想象的更为精确。这促使我们评估暗视觉是否接近 rod 时间分辨率限制。
