School of Engineering and Applied Science, Yale University, New Haven, CT, USA.
Interdepartmental Neuroscience Program, Yale University, New Haven, CT, USA.
Nat Neurosci. 2019 Aug;22(8):1318-1326. doi: 10.1038/s41593-019-0443-y. Epub 2019 Jul 25.
Direction-selective neurons respond to visual motion in a preferred direction. They are direction-opponent if they are also inhibited by motion in the opposite direction. In flies and vertebrates, direction opponency has been observed in second-order direction-selective neurons, which achieve this opponency by subtracting signals from first-order direction-selective cells with opposite directional tunings. Here, we report direction opponency in Drosophila that emerges in first-order direction-selective neurons, the elementary motion detectors T4 and T5. This opponency persists when synaptic output from these cells is blocked, suggesting that it arises from feedforward, not feedback, computations. These observations exclude a broad class of linear-nonlinear models that have been proposed to describe direction-selective computations. However, they are consistent with models that include dynamic nonlinearities. Simulations of opponent models suggest that direction opponency in first-order motion detectors improves motion discriminability by suppressing noise generated by the local structure of natural scenes.
方向选择性神经元对视觉运动的偏好方向做出反应。如果它们还受到相反方向运动的抑制，那么它们就是方向拮抗的。在苍蝇和脊椎动物中，二阶方向选择性神经元中观察到了方向拮抗，它们通过从具有相反方向调谐的一阶方向选择性细胞中减去信号来实现这种拮抗。在这里，我们报告了果蝇中出现的一阶方向选择性神经元 T4 和 T5 中的方向拮抗。当这些细胞的突触输出被阻断时，这种拮抗仍然存在，这表明它是由前馈而不是反馈计算引起的。这些观察结果排除了一类广泛的线性-非线性模型，这些模型被提出用于描述方向选择性计算。然而，它们与包括动态非线性的模型是一致的。对手模型的模拟表明，一阶运动探测器中的方向拮抗通过抑制自然场景局部结构产生的噪声来提高运动可分辨性。
