School of Natural Sciences, Institute for Advanced Study, Princeton, NJ 08540.
Center for Neural Science, New York University, New York, NY 10003.
Proc Natl Acad Sci U S A. 2021 Aug 10;118(32). doi: 10.1073/pnas.2105062118.
This paper offers a theory for the origin of direction selectivity (DS) in the macaque primary visual cortex, V1. DS is essential for the perception of motion and control of pursuit eye movements. In the macaque visual pathway, neurons with DS first appear in V1, in the Simple cell population of the Magnocellular input layer 4Cα. The lateral geniculate nucleus (LGN) cells that project to these cortical neurons, however, are not direction selective. We hypothesize that DS is initiated in feed-forward LGN input, in the summed responses of LGN cells afferent to a cortical cell, and it is achieved through the interplay of 1) different visual response dynamics of ON and OFF LGN cells and 2) the wiring of ON and OFF LGN neurons to cortex. We identify specific temporal differences in the ON/OFF pathways that, together with item 2, produce distinct response time courses in separated subregions; analysis and simulations confirm the efficacy of the mechanisms proposed. To constrain the theory, we present data on Simple cells in layer 4Cα in response to drifting gratings. About half of the cells were found to have high DS, and the DS was broadband in spatial and temporal frequency (SF and TF). The proposed theory includes a complete analysis of how stimulus features such as SF and TF interact with ON/OFF dynamics and LGN-to-cortex wiring to determine the preferred direction and magnitude of DS.
本文提出了一种关于猕猴初级视皮层 V1 中方向选择性（DS）起源的理论。DS 对于运动感知和追逐眼球运动的控制至关重要。在猕猴视觉通路中，具有 DS 的神经元首先出现在 V1 的大细胞输入层 4Cα 的简单细胞群体中。然而，投射到这些皮层神经元的外侧膝状体核（LGN）细胞没有 DS。我们假设 DS 是在视前馈 LGN 输入中发起的，在皮层细胞传入的 LGN 细胞的总和反应中，通过以下两种方式实现：1）ON 和 OFF LGN 细胞的不同视觉反应动力学，以及 2）ON 和 OFF LGN 神经元到皮层的连接。我们确定了 ON/OFF 通路中的特定时间差异，这些差异与第 2 点一起，在分离的子区域中产生不同的反应时程；分析和模拟证实了所提出机制的有效性。为了限制理论，我们提出了关于层 4Cα 中对漂移光栅反应的简单细胞的数据。发现大约一半的细胞具有高 DS，DS 在空间和时间频率（SF 和 TF）上是宽带的。所提出的理论包括对刺激特征（如 SF 和 TF）如何与 ON/OFF 动力学以及 LGN 到皮层的连接相互作用以确定 DS 的优势方向和幅度进行完整分析。
