该课题组之前的系列工作发现（Chen et al., Neuron 2014; Yan et al., Nature Neuroscience 2014），当视觉系统处理和整合大范围的视觉轮廓信息时，一方面V1可以通过皮层内部的长距离水平连接将局部的信息进行整合；另一方面相对较高级的视觉皮层V4可以利用V1上传的局部朝向信息快速组装成一个粗略的全局模板，进而通过反馈连接调节V1的整合过程，使得轮廓信号快速在不同等级的皮层中同时被放大。然而在这一加工过程中，来自V4的反馈信号与V1内部的水平连接之间如何相互作用仍不清楚。利用条件因果分析的方法（conditional Granger causality analysis），该研究发现，去除V4的反馈影响作用后，V1内部神经元间的相互驱动强度大大降低；此外，无论是去除对轮廓还是对背景反应的V1神经元的影响作用后，源于V4的反馈调控强度同样会大幅度下降。这些结果揭示了皮层内部的水平连接和皮层之间的反馈调节在图像信息整合中的协同作用。
Relative contributions of V4 feedback modulations and V1 lateral interactions to the contour integration process in V1. (A) Granger causality of spiking interactions between V1 contour sites (red) as compared to that without the influences from V4 sites (blue) or V1 background sites (magenta). (B) Granger causality of spiking interactions between V1 background sites (red) as compared to that without the influences from V4 sites (blue) or V1 contour sites (magenta). (C) Same data in A and B are replotted to show percent reductions in Granger causality after discounting V4 feedback or V1 lateral influences. Shaded areas and error bars represent ±SEM. (From Liang et el., 2017, PNAS, 114(32): 8637-8642)
Liang, H., X. Gong, M. Chen, Y. Yan, W. Li* and C. D. Gilbert* (2017). "Interactions between feedback and lateral connections in the primary visual cortex." Proceedings of the National Academy of Sciences 114(32): 8637-8642.
