Howard Hughes Medical Institute, Department of Integrative Biology and Physiology, University of California, Los Angeles, Los Angeles, CA 90095, USA.
Curr Biol. 2012 Mar 20;22(6):482-7. doi: 10.1016/j.cub.2012.01.044. Epub 2012 Mar 1.
Visual figures may be distinguished based on elementary motion or higher-order non-Fourier features, and flies track both. The canonical elementary motion detector, a compact computation for Fourier motion direction and amplitude, can also encode higher-order signals provided elaborate preprocessing. However, the way in which a fly tracks a moving figure containing both elementary and higher-order signals has not been investigated. Using a novel white noise approach, we demonstrate that (1) the composite response to an object containing both elementary motion (EM) and uncorrelated higher-order figure motion (FM) reflects the linear superposition of each component; (2) the EM-driven component is velocity-dependent, whereas the FM component is driven by retinal position; (3) retinotopic variation in EM and FM responses are different from one another; (4) the FM subsystem superimposes saccadic turns upon smooth pursuit; and (5) the two systems in combination are necessary and sufficient to predict the full range of figure tracking behaviors, including those that generate no EM cues at all. This analysis requires an extension of the model that fly motion vision is based on simple elementary motion detectors and provides a novel method to characterize the subsystems responsible for the pursuit of visual figures.
可以根据基本运动或高阶非傅里叶特征来区分视觉图形，而苍蝇则可以跟踪这两种特征。经典的基本运动探测器是一种用于傅里叶运动方向和幅度的紧凑计算，也可以提供精细预处理的高阶信号进行编码。然而，苍蝇如何跟踪包含基本运动和高阶运动的移动图形尚未得到研究。使用一种新颖的白噪声方法，我们证明了（1）包含基本运动（EM）和不相关高阶图形运动（FM）的物体的复合响应反映了每个分量的线性叠加；（2）EM 驱动的分量与速度有关，而 FM 分量则由视网膜位置驱动；（3）EM 和 FM 响应的视网膜拓扑变化彼此不同；（4）FM 子系统在平滑追踪上叠加扫视转弯；以及（5）这两个系统的组合是预测图形跟踪行为的必要和充分条件，包括那些根本不产生 EM 线索的行为。这种分析需要扩展苍蝇运动视觉基于简单基本运动探测器的模型，并提供一种新的方法来描述负责视觉图形追踪的子系统。
