Fly eyes are not still: a motion illusion in Drosophila flight supports parallel visual processing [RESEARCH ARTICLE]

Wael Salem, Benjamin Cellini, Mark A. Frye, and Jean-Michel Mongeau
Most animals shift gaze by a ‘fixate and saccade’ strategy, where the fixation phase stabilizes background motion. A logical prerequisite for robust detection and tracking of moving foreground objects, therefore, is to suppress the perception of background motion. In a virtual reality magnetic tether system enabling free yaw movement, Drosophila implemented a fixate and saccade strategy in the presence of a static panorama. When the spatial wavelength of a vertical grating was below the Nyquist wavelength of the compound eyes, flies drifted continuously and gaze could not be maintained at a single location. Because the drift occurs from a motionless stimulus – thus any perceived motion stimuli are generated by the fly itself – it is illusory, driven by perceptual aliasing. Notably, the drift speed was significantly faster than under a uniform panorama, suggesting perceptual enhancement as a result of aliasing. Under the same visual conditions in a rigid-tether paradigm, wing steering responses to the unresolvable static panorama were not distinguishable from those to a resolvable static pattern, suggesting visual aliasing is induced by ego motion. We hypothesized that obstructing the control of gaze fixation also disrupts detection and tracking of objects. Using the illusory motion stimulus, we show that magnetically tethered Drosophila track objects robustly in flight even when gaze ...

Source: Journal of Experimental Biology - May 27, 2020 Category: Biology Authors: Salem, W., Cellini, B., Frye, M. A., Mongeau, J.-M. Tags: RESEARCH ARTICLE Source Type: research