Figure Tracking by Flies Is Supported by Parallel Visual Streams

SummaryVisual figures may be distinguished based on elementary motion or higher-order non-Fourier features, and flies track both [1]. The canonical elementary motion detector, a compact computation for Fourier motion direction and amplitude, can also encode higher-order signals provided elaborate preprocessing [2, 3 and 4]. 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 [1]. This analysis requires an extension of the model that fly motion vision is based on simple elementary motion detectors [5] and provides a novel method to characterize the subsystems responsible for the pursuit of visual figures.

Graphical AbstractFigure optionsDownload high-quality image (286 K)Download as PowerPoint slideHighlights
► Visual figures are distinguished by coherent motion and higher order spatial features
► We used a white noise approach to decouple and analyze these two components
► Flies have independent subsystems to track each stream, differing in space and time
► Filters that describe the two streams robustly predict visual figure tracking