Department of Mechanical Engineering, Pennsylvania State University, University Park, PA 16802, USA.
Department of Integrative Biology and Physiology, University of California - Los Angeles, Los Angeles, CA 90095-7239, USA.
J Exp Biol. 2020 May 28;223(Pt 10):jeb212316. doi: 10.1242/jeb.212316.
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, 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 track objects robustly in flight even when gaze is not fixated as flies continuously drift. Taken together, our study provides further support for parallel visual motion processing and reveals the critical influence of body motion on visuomotor processing. Motion illusions can reveal important shared principles of information processing across taxa.
大多数动物通过“注视和扫视”策略来转移目光，其中注视阶段稳定背景运动。因此，稳健检测和跟踪移动前景物体的逻辑前提是抑制对背景运动的感知。在允许自由偏航运动的虚拟现实磁系绳系统中，研究人员在存在静态全景图的情况下实施了注视和扫视策略。当垂直光栅的空间波长低于复眼的奈奎斯特波长时，苍蝇会持续漂移，无法将目光保持在单个位置。由于漂移发生在静止的刺激物上 - 因此任何感知到的运动刺激都是由苍蝇本身产生的 - 它是虚幻的，是由感知混叠驱动的。值得注意的是，漂移速度明显快于均匀全景图下的速度，这表明混叠导致了增强。在刚性系绳范式下相同的视觉条件下，对不可分辨的静态全景图的翅膀转向反应与可分辨的静态图案的反应没有区别，这表明视觉混叠是由自我运动引起的。我们假设，阻碍注视固定的控制也会干扰物体的检测和跟踪。使用虚幻的运动刺激，我们表明即使在苍蝇持续漂移时，磁系绳也可以在飞行中稳健地跟踪物体，即使目光没有固定。总之，我们的研究为并行视觉运动处理提供了进一步的支持，并揭示了身体运动对视觉运动处理的关键影响。运动错觉可以揭示跨类群信息处理的重要共享原则。
