Grant Simon, Conway Miriam L
Applied Vision Research Centre, City, University of London, Northampton Square, London, EC1V 0HB, UK.
Exp Brain Res. 2019 May;237(5):1239-1255. doi: 10.1007/s00221-019-05503-4. Epub 2019 Mar 8.
Proficient (fast, accurate, precise) hand actions for reaching-to-grasp 3D objects are known to benefit significantly from the use of binocular vision compared to one eye alone. We examined whether these binocular advantages derive from increased reliability in encoding the goal object's properties for feedforward planning of prehension movements or from enhanced feedback mediating their online control. Adult participants reached for, precision grasped and lifted cylindrical table-top objects (two sizes, 2 distances) using binocular vision or only their dominant/sighting eye or their non-dominant eye to program and fully execute their movements or using each of the three viewing conditions only to plan their reach-to-grasp during a 1 s preview, with vision occluded just before movement onset. Various kinematic measures of reaching and grasping proficiency, including corrective error rates, were quantified and compared by view, feedback and object type. Some significant benefits of binocular over monocular vision when they were just available for pre-movement planning were retained for the reach regardless of target distance, including higher peak velocities, straighter paths and shorter low velocity approach times, although these latter were contaminated by more velocity corrections and by poorer coordination with object contact. By contrast, virtually all binocular advantages for grasping, including improvements in peak grip aperture scaling, the accuracy and precision of digit placements at object contact and shorter grip application times preceding the lift, were eliminated with no feedback available, outcomes that were influenced by the object's size. We argue that vergence cues can improve the reliability of binocular internal representations of object distance for the feedforward programming of hand transport, whereas the major benefits of binocular vision for enhancing grasping performance derive exclusively from its continuous presence online.
众所周知，与单眼相比，在伸手抓取三维物体时，熟练（快速、准确、精确）的手部动作能从双眼视觉的使用中显著受益。我们研究了这些双眼优势是源于在为抓握动作的前馈规划对目标物体属性进行编码时可靠性的提高，还是源于增强的反馈对其在线控制的调节。成年参与者使用双眼视觉、仅用其优势眼/注视眼或非优势眼来规划并完全执行他们的动作，伸手去精准抓握并提起圆柱形桌面物体（两种尺寸，两个距离），或者仅在1秒的预视期间使用这三种视觉条件中的每一种来规划他们的伸手抓取动作，在动作开始前遮挡视觉。通过视觉、反馈和物体类型对包括纠正错误率在内的各种伸手和抓握熟练度的运动学指标进行了量化和比较。当双眼视觉仅用于运动前规划时，无论目标距离如何，在伸手动作中双眼视觉相对于单眼视觉的一些显著优势得以保留，包括更高的峰值速度、更直的路径和更短的低速接近时间，尽管后者受到更多速度校正以及与物体接触时协调性较差的影响。相比之下，在没有反馈的情况下，几乎所有抓握动作的双眼优势都消失了，包括峰值握距缩放的改善、物体接触时手指放置的准确性和精度以及提起前更短的握力施加时间，这些结果受到物体尺寸的影响。我们认为，聚散线索可以提高双眼对物体距离内部表征的可靠性，用于手部运输的前馈编程，而双眼视觉对增强抓握性能的主要益处完全源于其在在线过程中的持续存在。
