Denman Daniel J, Siegle Joshua H, Koch Christof, Reid R Clay, Blanche Timothy J
Allen Institute for Brain Science, Seattle, Washington 98109
Allen Institute for Brain Science, Seattle, Washington 98109.
J Neurosci. 2017 Feb 1;37(5):1102-1116. doi: 10.1523/JNEUROSCI.1742-16.2016. Epub 2016 Dec 16.
In both dichromats and trichromats, cone opsin signals are maintained independently in cones and combined at the bipolar and retinal ganglion cell level, creating parallel color opponent pathways to the central visual system. Like other dichromats, the mouse retina expresses a short-wavelength (S) and a medium-wavelength (M) opsin, with the S-opsin shifted to peak sensitivity in the ultraviolet (UV) range. Unlike in primates, nonuniform opsin expression across the retina and coexpression in single cones creates a mostly mixed chromatic signal. Here, we describe the visuotopic and chromatic organization of spiking responses in the dorsal lateral geniculate and of the local field potentials in their recipient zone in primary visual cortex (V1). We used an immersive visual stimulus dome that allowed us to present spatiotemporally modulated UV and green luminance in any region of the visual field of an awake, head-fixed mouse. Consistent with retinal expression of opsins, we observed graded UV-to-green dominated responses from the upper to lower visual fields, with a smaller difference across azimuth. In addition, we identified a subpopulation of cells (<10%) that exhibited spectrally opponent responses along the S-M axis. Luminance signals of each wavelength and color signals project to the middle layers of V1.
In natural environments, color information is useful for guiding behavior. How small terrestrial mammals such as mice use graded expression of cone opsins to extract visual information from their environments is not clear, even as the use of mice for studying visually guided behavior grows. In this study, we examined the color signals that the retina sends to the visual cortex via the lateral geniculate nucleus of the thalamus. We found that green dominated responses in the lower and nasal visual field and ultraviolet dominated responses in the upper visual field. We describe a subset of cells that exhibit color opponent responses.
在二色视者和三色视者中，视锥蛋白信号在视锥细胞中独立维持，并在双极细胞和视网膜神经节细胞水平上合并，形成通向中枢视觉系统的平行颜色拮抗通路。与其他二色视者一样，小鼠视网膜表达一种短波长（S）和一种中波长（M）视蛋白，S视蛋白的峰值敏感性转移到紫外线（UV）范围内。与灵长类动物不同，视网膜上视蛋白表达不均匀以及在单个视锥细胞中共表达会产生主要为混合色信号。在这里，我们描述了背侧外侧膝状体中尖峰反应的视拓扑和颜色组织，以及初级视觉皮层（V1）中其接收区域的局部场电位。我们使用了一个沉浸式视觉刺激圆顶，使我们能够在清醒、头部固定的小鼠视野的任何区域呈现时空调制的紫外线和绿色亮度。与视蛋白在视网膜中的表达一致，我们观察到从视野上部到下部的紫外线到绿色主导的分级反应，在方位角上的差异较小。此外，我们确定了一个细胞亚群（<10%），它们沿S-M轴表现出光谱拮抗反应。每个波长的亮度信号和颜色信号投射到V1的中层。
在自然环境中，颜色信息有助于指导行为。尽管将小鼠用于研究视觉引导行为的情况越来越多，但像小鼠这样的小型陆生哺乳动物如何利用视锥蛋白的分级表达从其环境中提取视觉信息尚不清楚。在这项研究中，我们研究了视网膜通过丘脑外侧膝状体核发送到视觉皮层的颜色信号。我们发现绿色在下部和鼻侧视野中占主导反应，而紫外线在上部视野中占主导反应。我们描述了一组表现出颜色拮抗反应的细胞。
