Cowan Cameron S, Sabharwal Jasdeep, Seilheimer Robert L, Wu Samuel M
Baylor College of Medicine, Department of Ophthalmology, United States; Baylor College of Medicine, Department of Neuroscience, United States.
Baylor College of Medicine, Department of Ophthalmology, United States; Baylor College of Medicine, Department of Neuroscience, United States.
Vision Res. 2017 Feb;131:96-105. doi: 10.1016/j.visres.2016.12.015. Epub 2017 Jan 24.
The remarkable dynamic range of vision is facilitated by adaptation of retinal sensitivity to ambient lighting conditions. An important mechanism of sensitivity adaptation is control of the spatial and temporal window over which light is integrated. The retina accomplishes this by switching between parallel synaptic pathways with differing kinetics and degrees of synaptic convergence. However, the relative shifts in spatial and temporal integration are not well understood - particularly in the context of the antagonistic spatial surround. Here, we resolve these issues by characterizing the adaptation-induced changes to spatiotemporal integration in the linear receptive field center and surround of mouse retinal ganglion cells. While most ganglion cells lose their antagonistic spatial surround under scotopic conditions, a strong surround is maintained in a subset. We then applied a novel technique that allowed us to analyze the receptive field as a triphasic temporal filter in the center and a biphasic filter in the surround. The temporal tuning of the surround was relatively maintained across adaptation conditions compared to the center, which greatly increased its temporal integration. Though all phases of the center's triphasic temporal response slowed, some shifted significantly less. Additionally, adaptation differentially shifted ON and OFF pathway temporal tuning, reducing their asymmetry under scotopic conditions. Finally, spatial integration was significantly increased by dark adaptation in some cells while it decreased it in others. These findings provide novel insight into how adaptation adjusts visual information processing by altering fundamental properties of ganglion cell receptive fields, such as center-surround antagonism and space-time integration.
视网膜对环境光照条件的敏感度适应有助于实现卓越的视觉动态范围。敏感度适应的一个重要机制是控制光整合的空间和时间窗口。视网膜通过在具有不同动力学和突触汇聚程度的平行突触通路之间切换来实现这一点。然而，空间和时间整合的相对变化尚不清楚，尤其是在拮抗空间环绕的背景下。在这里，我们通过表征小鼠视网膜神经节细胞线性感受野中心和环绕区域中适应诱导的时空整合变化来解决这些问题。虽然大多数神经节细胞在暗视条件下失去了拮抗空间环绕，但仍有一部分细胞保持着强烈的环绕。然后，我们应用了一种新技术，使我们能够将感受野分析为中心的三相时间滤波器和环绕区域的双相滤波器。与中心相比，环绕区域的时间调谐在不同适应条件下相对保持稳定，这大大增加了其时间整合。虽然中心三相时间响应的所有阶段都变慢了，但有些阶段的变化明显较小。此外，适应对ON和OFF通路的时间调谐产生了不同的影响，减少了它们在暗视条件下的不对称性。最后，暗适应在一些细胞中显著增加了空间整合，而在另一些细胞中则降低了空间整合。这些发现为适应如何通过改变神经节细胞感受野的基本特性（如中心-环绕拮抗和时空整合）来调整视觉信息处理提供了新的见解。
