Department of Ophthalmology and Visual Science, Moran Eye Institute, University of Utah, Salt Lake City, Utah 84132.
Department of Ophthalmology and Visual Science, Moran Eye Institute, University of Utah, Salt Lake City, Utah 84132
J Neurosci. 2019 Sep 18;39(38):7501-7512. doi: 10.1523/JNEUROSCI.1096-19.2019. Epub 2019 Jul 29.
In macaque visual cortex, different cytochrome oxidase stripes of area V2 receive segregated projections from layers (L)2/3 and 4B of the primary visual cortex (V1), and project to dorsal or ventral stream extrastriate areas. Parallel V1-to-V2 pathways suggest functionally specialized circuits, but it is unknown whether these circuits arise from distinct cell types. V1 L4B includes two morphological types of excitatory projection neurons: pyramids, which carry mixed magnocellular (M) and parvocellular (P) information to downstream areas, and spiny stellates, which carry only M information. Previous studies have shown that, overall, V2 receives ∼80% of its L4B inputs from pyramids, thus receiving mixed M and P signals. However, it is unknown how pyramids and stellates distribute their outputs to the different V2 stripes, and whether different stripes receive inputs from morphologically distinct neuron types. Using viral-mediated labeling of V2-projecting L4B neurons in male macaques, we show that thick stripes receive a greater contribution of L4B inputs from M-dominated spiny stellates compared with thin stripes. Both stripe types, however, receive a much larger contribution from spiny stellates than previously shown for V2 overall, indicating that a larger amount of M information than previously thought flows into both the dorsal and ventral streams via the V2 thick and thin stripes, respectively. Moreover, we identify four types of V2-projecting L4B cells differing in size and complexity. Three such cell types project to both thin and thick stripes, but one type, the giant spiny-stellate neuron, resembling L4B neurons projecting to motion-sensitive area MT, was only found to project to thick stripes. Area V1 partitions visual information into functionally specialized parallel pathways which terminate into distinct stripes of area V2. We asked whether V1 inputs to different V2 stripes arise from morphologically different cell types. V1 layer (L)4B has two cell types: pyramids, which carry both magnocellular (M) and parvocellular (P) visual signals, and spiny stellates, which carry only M signals. We find that V2 thick stripes, which project to areas processing object motion, receive a larger fraction of L4B input from M-dominated stellates compared with thin stripes, which project to areas processing object attributes. We also identify four morphological types of V2-projecting L4B neurons, suggestive of four functionally specialized cell types.
在猕猴的视觉皮层中，V2 的不同细胞色素氧化酶纹接收来自初级视觉皮层（V1）的 L2/3 和 4B 层的分离投射，并投射到背侧或腹侧流的外纹状区。平行的 V1-V2 通路表明存在功能特化的回路，但尚不清楚这些回路是否来自不同的细胞类型。V1 的 L4B 包括两种形态类型的兴奋性投射神经元：金字塔，它们携带混合的大细胞（M）和小细胞（P）信息到下游区域，和棘突星状细胞，它们只携带 M 信息。先前的研究表明，总的来说，V2 从金字塔接收其 L4B 输入的约 80%，因此接收混合的 M 和 P 信号。然而，目前尚不清楚金字塔和星状细胞如何将其输出分配到不同的 V2 纹，以及不同的纹是否接收来自形态上不同的神经元类型的输入。使用雄性猕猴中 V2 投射的 L4B 神经元的病毒介导标记，我们表明厚纹比薄纹从 M 主导的棘突星状细胞接收更多的 L4B 输入。然而，两种纹类型都比以前的 V2 整体接收来自棘突星状细胞的更大贡献，这表明比以前认为的更多的 M 信息分别通过 V2 的厚和薄纹流入背侧和腹侧流。此外，我们鉴定了四种不同大小和复杂性的 V2 投射 L4B 细胞类型。这三种细胞类型都投射到薄和厚纹，但一种类型，即巨大的棘突星状神经元，类似于投射到运动敏感区 MT 的 L4B 神经元，仅发现投射到厚纹。V1 将视觉信息分割成功能特化的平行通路，这些通路终止于不同的 V2 纹。我们询问不同 V2 纹的 V1 输入是否来自形态上不同的细胞类型。V1 层（L）4B 有两种细胞类型：金字塔，携带大细胞（M）和小细胞（P）视觉信号，和棘突星状细胞，只携带 M 信号。我们发现，与投射到处理物体属性的区域的薄纹相比，投射到处理物体运动的区域的 V2 厚纹从 M 主导的星状细胞接收更大比例的 L4B 输入。我们还鉴定了四种形态类型的 V2 投射 L4B 神经元，暗示了四种功能特化的细胞类型。
