Center for Vision Research and State University of New York (SUNY) Eye Institute, Department of Ophthalmology, SUNY Upstate Medical University, Syracuse, New York 13210, USA.
J Neurosci. 2012 Oct 10;32(41):14364-73. doi: 10.1523/JNEUROSCI.1296-12.2012.
The rate at which photoreceptors recover from excitation is thought to be critical for setting the temporal resolution of vision. Indeed, mutations in RGS9 (regulator of G-protein signaling 9) and R9AP (RGS9 anchor protein) proteins mediating rapid photoresponse recovery impair patients' ability to see moving objects. In this study, we analyzed temporal properties of retinal sensitivity and spatiotemporal aspects of visual behavior in R9AP knock-out mice. Surprisingly, we have found that this knock-out does not affect dim-light vision mediated by rods acting as single-photon counters. Under these conditions, vision was also unaffected in mice overexpressing R9AP in rods, which causes accelerated photoresponse recovery. However, in brighter light, slow photoresponse recovery in rods and cones impaired visual responses to high temporal frequency stimuli, as reported for the daylight vision of human patients. Therefore, the speed of photoresponse recovery can affect temporal resolution and motion detection when photoreceptors integrate signals from multiple photons but not when they act as single-photon counters.
光感受器从兴奋中恢复的速度被认为对视觉的时间分辨率至关重要。事实上，介导快速光反应恢复的 RGS9（G 蛋白信号转导调节因子 9）和 R9AP（RGS9 锚蛋白）蛋白的突变会损害患者识别移动物体的能力。在这项研究中，我们分析了 R9AP 敲除小鼠视网膜敏感性的时间特性和视觉行为的时空方面。令人惊讶的是，我们发现这种敲除不会影响作为单光子计数器的视杆细胞介导的暗光视觉。在这些条件下，在视杆细胞中过表达 R9AP 的小鼠的视觉也不受影响，这会导致光反应恢复加速。然而，在更亮的光线下，视杆细胞和视锥细胞的光反应恢复缓慢会损害对高时间频率刺激的视觉反应，这正如人类患者的日光视觉所报告的那样。因此，当光感受器整合来自多个光子的信号时，光反应恢复的速度会影响时间分辨率和运动检测，但当它们作为单光子计数器时则不会。
