Pearson James T, Kerschensteiner Daniel
Department of Ophthalmology and Visual Sciences, Washington University School of Medicine, St. Louis, Missouri; Graduate Program in Developmental, Regenerative and Stem Cell Biology, Washington University School of Medicine, St. Louis, Missouri;
Department of Ophthalmology and Visual Sciences, Washington University School of Medicine, St. Louis, Missouri; Department of Anatomy and Neurobiology, Washington University School of Medicine, St. Louis, Missouri; and Hope Center for Neurological Disorders at Washington University School of Medicine, St. Louis, Missouri
J Neurophysiol. 2015 Jul;114(1):540-50. doi: 10.1152/jn.00360.2015. Epub 2015 May 20.
Contrast, a fundamental feature of visual scenes, is encoded in a distributed manner by ∼ 20 retinal ganglion cell (RGC) types, which stream visual information to the brain. RGC types respond preferentially to positive (ON(pref)) or negative (OFF(pref)) contrast and differ in their sensitivity to preferred contrast and responsiveness to nonpreferred stimuli. Vision operates over an enormous range of mean light levels. The influence of ambient illumination on contrast encoding across RGC types is not well understood. Here, we used large-scale multielectrode array recordings to characterize responses of mouse RGCs under lighting conditions spanning five orders in brightness magnitude. We identify three functional RGC types that switch contrast preference in a luminance-dependent manner (Sw1-, Sw2-, and Sw3-RGCs). As ambient illumination increases, Sw1- and Sw2-RGCs shift from ON(pref) to OFF(pref) and Sw3-RGCs from OFF(pref) to ON(pref). In all cases, transitions in contrast preference are reversible and track light levels. By mapping spatiotemporal receptive fields at different mean light levels, we find that changes in input from ON and OFF pathways in receptive field centers underlie shifts in contrast preference. Sw2-RGCs exhibit direction-selective responses to motion stimuli. Despite changing contrast preference, direction selectivity of Sw2-RGCs and other RGCs as well as orientation-selective responses of RGCs remain stable across light levels.
对比度作为视觉场景的一个基本特征，由约20种视网膜神经节细胞（RGC）类型以分布式方式进行编码，这些细胞将视觉信息传输到大脑。不同类型的RGC对正对比度（ON（pref））或负对比度（OFF（pref））有优先反应，并且在对偏好对比度的敏感度和对非偏好刺激的反应性方面存在差异。视觉在极大范围的平均光照水平下发挥作用。环境光照对不同类型RGC对比度编码的影响尚未得到充分理解。在这里，我们使用大规模多电极阵列记录来表征小鼠RGC在跨越五个亮度量级的光照条件下的反应。我们识别出三种功能性RGC类型，它们以亮度依赖的方式切换对比度偏好（Sw1 -、Sw2 - 和Sw3 - RGC）。随着环境光照增加，Sw1 - 和Sw2 - RGC从ON（pref）转变为OFF（pref），而Sw3 - RGC从OFF（pref）转变为ON（pref）。在所有情况下，对比度偏好的转变都是可逆的并且跟踪光照水平。通过绘制不同平均光照水平下的时空感受野，我们发现感受野中心ON和OFF通路输入的变化是对比度偏好转变的基础。Sw2 - RGC对运动刺激表现出方向选择性反应。尽管对比度偏好发生变化，但Sw2 - RGC和其他RGC的方向选择性以及RGC的方向选择性反应在不同光照水平下保持稳定。
