In spite of their anatomical robustness, it has been difficult to establish the functional role of corticogeniculate circuits connecting primary visual cortex with the lateral geniculate nucleus of the thalamus (LGN) in the feedback direction. Growing evidence suggests that corticogeniculate feedback does not directly shape the spatial receptive field properties of LGN neurons, but rather regulates the timing and precision of LGN responses and the information coding capacity of LGN neurons. We propose that corticogeniculate feedback specifically stabilizes the response gain of LGN neurons, thereby increasing their information coding capacity. Inspired by early work by McClurkin et al. (1994), we manipulated the activity of corticogeniculate neurons to test this hypothesis. We used optogenetic methods to selectively and reversibly enhance the activity of corticogeniculate neurons in anesthetized ferrets while recording responses of LGN neurons to drifting gratings and white noise stimuli. We found that optogenetic activation of corticogeniculate feedback systematically reduced LGN gain variability and increased information coding capacity among LGN neurons. Optogenetic activation of corticogeniculate neurons generated similar increases in information encoded in LGN responses to drifting gratings and white noise stimuli. Together, these findings suggest that the influence of corticogeniculate feedback on LGN response precision and information coding capacity could be mediated through reductions in gain variability.

尽管它们在解剖学上具有稳健性，但很难确定皮质原状电路在反馈方向上连接初级视觉皮层与丘脑外侧膝状体核 (LGN) 的功能作用。越来越多的证据表明，皮质源性反馈并不直接影响 LGN 神经元的空间感受野特性，而是调节 LGN 反应的时间和精度以及 LGN 神经元的信息编码能力。我们建议皮质源性反馈专门稳定 LGN 神经元的响应增益，从而提高它们的信息编码能力。受 McClurkin 等人早期工作的启发。（1994），我们操纵了皮质原神经元的活动来检验这个假设。我们使用光遗传学方法选择性和可逆地增强麻醉雪貂中皮质生成神经元的活性，同时记录 LGN 神经元对漂移光栅和白噪声刺激的反应。我们发现皮质源性反馈的光遗传学激活系统地降低了 LGN 增益变异性并增加了 LGN 神经元之间的信息编码能力。皮质化神经元的光遗传学激活在 LGN 对漂移光栅和白噪声刺激的反应中编码的信息产生了类似的增加。总之，这些研究结果表明，皮质源性反馈对 LGN 反应精度和信息编码能力的影响可以通过降低增益变异性来调节。