In primates and carnivores, the main laminae of the dorsal lateral geniculate nucleus (LGN) receive monocular excitatory input in an eye-alternating fashion. There is also evidence that nondominant eye stimulation can reduce responses to dominant eye stimulation and that a subset of LGN cells in the koniocellular (K) layers receives convergent binocular excitatory input from both eyes. What is not known is how the two eye inputs summate in the K layers of LGN. Here, we aimed to answer this question by making extracellular array electrode recordings targeted to K layers in the marmoset (Callithrix jacchus) LGN, as visual stimuli (flashed 200 ms temporal square-wave pulses or drifting gratings) were presented to each eye independently or to both eyes simultaneously. We found that when the flashed stimulus was presented to both eyes, compared to the dominant eye, the peak firing rate of most cells (61%, 14/23) was reduced. The remainder showed response facilitation (17%) or partial summation (22%). A greater degree of facilitation was seen when the total number of spikes across the stimulus time window (200 ms) rather than peak firing rates was measured. A similar pattern of results was seen for contrast-varying gratings and for small numbers of parvocellular (n = 12) and magnocellular (n = 3) cells recorded. Our findings show that binocular summation in the marmoset LGN is weak and predominantly sublinear in nature.

中文翻译：

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狨猴外侧膝状体核的双眼总和

在灵长类动物和食肉动物中，背外侧膝状体核 (LGN) 的主层以交替的方式接收单眼兴奋性输入。还有证据表明，非优势眼刺激可以减少对优势眼刺激的反应，并且 koniocellular (K) 层中的 LGN 细胞子集接收来自双眼的会聚双眼兴奋性输入。未知的是两个眼图输入如何在 LGN 的 K 层中求和。在这里，我们旨在通过针对狨猴的 K 层进行细胞外阵列电极记录来回答这个问题（马蹄莲） LGN，作为视觉刺激（闪烁的 200 ms 时间方波脉冲或漂移光栅）独立地呈现给每只眼睛或同时呈现给双眼。我们发现，当向双眼呈现闪光刺激时，与优势眼相比，大多数细胞的峰值放电率（61%，14/23）降低了。其余显示响应促进（17%）或部分总结（22%）。当测量刺激时间窗口（200 ms）上的峰值总数而不是峰值发射率时，可以看到更大程度的促进作用。对于对比度变化的光栅和少量的细小细胞（n= 12) 和大细胞 (n= 3) 记录的细胞。我们的研究结果表明，狨猴 LGN 中的双目总和是弱的，并且本质上主要是亚线性的。