Department of Neuroscience, Psychology and Behaviour, University of Leicester , Leicester , United Kingdom.
Faculté de Psychologie et des Sciences de l'Education, University of Geneva , Geneva , Switzerland.
J Neurophysiol. 2019 May 1;121(5):1787-1797. doi: 10.1152/jn.00591.2018. Epub 2019 Mar 6.
Smooth pursuit eye movements (pursuit) are used to minimize the retinal motion of moving objects. During pursuit, the pattern of motion on the retina carries not only information about the object movement but also reafferent information about the eye movement itself. The latter arises from the retinal flow of the stationary world in the direction opposite to the eye movement. To extract the global direction of motion of the tracked object and stationary world, the visual system needs to integrate ambiguous local motion measurements (i.e., the aperture problem). Unlike the tracked object, the stationary world's global motion is entirely determined by the eye movement and thus can be approximately derived from motor commands sent to the eye (i.e., from an efference copy). Because retinal motion opposite to the eye movement is dominant during pursuit, different motion integration mechanisms might be used for retinal motion in the same direction and opposite to pursuit. To investigate motion integration during pursuit, we tested direction discrimination of a brief change in global object motion. The global motion stimulus was a circular array of small static apertures within which one-dimensional gratings moved. We found increased coherence thresholds and a qualitatively different reflexive ocular tracking for global motion opposite to pursuit. Both effects suggest reduced sampling of motion opposite to pursuit, which results in an impaired ability to extract coherence in motion signals in the reafferent direction. We suggest that anisotropic motion integration is an adaptation to asymmetric retinal motion patterns experienced during pursuit eye movements. This study provides a new understanding of how the visual system achieves coherent perception of an object's motion while the eyes themselves are moving. The visual system integrates local motion measurements to create a coherent percept of object motion. An analysis of perceptual judgments and reflexive eye movements to a brief change in an object's global motion confirms that the visual and oculomotor systems pick fewer samples to extract global motion opposite to the eye movement.
平滑追踪眼动（追踪）用于将移动物体的视网膜运动最小化。在追踪过程中，视网膜上的运动模式不仅携带有关物体运动的信息，还携带有关眼球运动本身的反馈信息。后者源自与眼球运动方向相反的静止世界的视网膜流动。为了提取被跟踪物体和静止世界的整体运动方向，视觉系统需要整合模糊的局部运动测量（即孔径问题）。与被跟踪的物体不同，静止世界的整体运动完全由眼球运动决定，因此可以从发送到眼睛的运动命令中近似得出（即，从传出副本得出）。由于在追踪过程中眼球运动的反向视网膜运动占主导地位，因此可能会使用不同的运动整合机制来处理相同方向和与追踪相反的视网膜运动。为了研究追踪过程中的运动整合，我们测试了短暂改变全局物体运动方向的辨别能力。全局运动刺激是一个小静态孔径的圆形阵列，其中一维光栅移动。我们发现，对于与追踪相反的全局运动，相干阈值增加并且反射性眼球追踪具有定性差异。这两种效应均表明，与追踪相反的运动采样减少，导致在反馈方向的运动信号中提取相干性的能力受损。我们认为各向异性的运动整合是对追踪眼球运动过程中经历的不对称视网膜运动模式的一种适应。本研究为视觉系统如何在眼睛运动时实现对物体运动的连贯感知提供了新的认识。视觉系统整合局部运动测量以创建对物体运动的连贯感知。对物体全局运动的短暂变化的感知判断和反射性眼球运动的分析证实，视觉和眼球运动系统提取与眼球运动相反的全局运动的样本较少。
