Fukui Takao, Inui Toshio
Department of Intelligence Science and Technology, Graduate School of Informatics, Kyoto University, Yoshida-Honmachi, Sakyo-ku, Kyoto 606-8501, Japan.
Hum Mov Sci. 2006 Jun;25(3):349-71. doi: 10.1016/j.humov.2006.02.002. Epub 2006 May 16.
Two experiments were conducted to investigate (1) during which phase of the movement vision is most critical for control, and (2) how vision of the target object and the participant's moving limb affect the control of grasping during that movement phase. In Experiment 1, participants, wearing liquid crystal shutter goggles, reached for and grasped a cylinder with a diameter of 4 or 6 cm under a shutting paradigm (SP) and a re-opening paradigm (RP). In SP, the goggles closed (turned opaque) 0 ms, 150 ms, 350 ms, 500 ms, or 700 ms after movement onset, or remained open (transparent) during the prehension movements. In RP, the goggles closed immediately upon movement onset, and re-opened 0 ms (i.e., without initially shutting), 150 ms, 350 ms, 500 ms, or 700 ms after the initial shutting, or remained opaque throughout the prehension movements. The duration of the prehension movements was kept relatively constant across participants and trials at approximately 1100 ms, i.e., the duration of prehension movements typically observed in daily life. The location of the target object was constant during the entire experiment. The SP and RP paradigms were counter-balanced across participants, and the order of conditions within each session was randomized. The main findings were that peak grip aperture (PGA) in the 150 ms-shutting condition was significantly larger than in the 350 ms-shutting condition, and that PGA in the 350 ms-re-opening condition was significantly larger than in the 150 ms-re-opening condition. These results revealed that online vision between 150 ms and 350 ms was critical for grasp control on PGA in typical, daily-life-speeded prehension movements. Furthermore, the results obtained for the time after maximal deceleration (TAMD; movement duration-time to maximal deceleration) demonstrated that early-phase vision contributed to the temporal pattern of the later movement phases (i.e., TAMD). The results thus demonstrated that online vision in the early phase of movement is crucial for the control of grasping. In addition to the apparatus used in Experiment 1, two liquid shutter plates placed in the same horizontal plane (25 cm above the experimental table) were used in Experiment 2 to manipulate the visibility of the target and the participant's moving limb. The plate closest to the participant altered vision of the limb/hand, while the more distant plate controlled vision of the object. The conditions were as follows: (1) both plates were open during movement (full vision condition); (2) both plates were closed 0, 150, or 350 ms following onset of arm movement (front-rear condition: FR); or (3) only the near plate closed 0, 150, or 350 ms following the onset of the arm movement (front condition: F). The results showed that shutting at 0 and 150 ms in the FR condition caused a significantly larger PGA, while the timing of shutting in the F condition had little influence on the PGA. These findings indicated that online vision, especially of the target object, during the early phase of prehension movements is critical to the control of grasping.
进行了两项实验，以研究：（1）在运动的哪个阶段，视觉对于控制最为关键；（2）目标物体和参与者移动肢体的视觉如何在该运动阶段影响抓握控制。在实验1中，参与者佩戴液晶快门眼镜，在关闭范式（SP）和重新打开范式（RP）下伸手抓取一个直径为4或6厘米的圆柱体。在SP中，眼镜在运动开始后0毫秒、150毫秒、350毫秒、500毫秒或700毫秒关闭（变为不透明），或者在抓握运动期间保持打开（透明）。在RP中，眼镜在运动开始时立即关闭，并在初始关闭后0毫秒（即不先关闭）、150毫秒、350毫秒、500毫秒或700毫秒重新打开，或者在整个抓握运动期间保持不透明。抓握运动的持续时间在参与者和试验中保持相对恒定，约为1100毫秒，即日常生活中通常观察到的抓握运动持续时间。在整个实验过程中，目标物体的位置保持不变。SP和RP范式在参与者之间进行了平衡，每个会话内条件的顺序是随机的。主要发现是，在150毫秒关闭条件下的峰值握距（PGA）显著大于350毫秒关闭条件下的PGA，并且在350毫秒重新打开条件下的PGA显著大于150毫秒重新打开条件下的PGA。这些结果表明，在150毫秒至350毫秒之间的在线视觉对于典型的、日常生活速度的抓握运动中PGA的抓握控制至关重要。此外，最大减速后时间（TAMD；运动持续时间 - 达到最大减速的时间）的结果表明，早期视觉有助于后期运动阶段的时间模式（即TAMD）。因此，结果表明运动早期的在线视觉对于抓握控制至关重要。除了实验1中使用的设备外，实验2中还使用了两个放置在同一水平平面（实验台上方25厘米）的液体快门板来操纵目标和参与者移动肢体的可见性。最靠近参与者的板改变肢体/手的视觉，而较远的板控制物体的视觉。条件如下：（1）运动期间两个板都打开（全视觉条件）；（2）手臂运动开始后0、150或350毫秒两个板都关闭（前后条件：FR）；或（3）手臂运动开始后0、150或350毫秒仅靠近的板关闭（前条件：F）。结果表明，在FR条件下0和150毫秒关闭会导致显著更大的PGA，而F条件下关闭的时间对PGA影响很小。这些发现表明，抓握运动早期的在线视觉，尤其是目标物体的视觉，对于抓握控制至关重要。
