Moizumi Shunjiro, Yamamoto Shinya, Kitazawa Shigeru
Department of Neurophysiology, Juntendo University Graduate School of Medicine, Tokyo 113-8421, Japan.
Neurosci Res. 2007 Sep;59(1):60-7. doi: 10.1016/j.neures.2007.05.013. Epub 2007 Jun 2.
When we touch something with a tool, we feel the touch at the tip of the tool rather than at the hand. Yamamoto and Kitazawa [Yamamoto, S., Kitazawa, S., 2001b. Sensation at the tips of invisible tools. Nat. Neurosci. 4, 979-980] previously showed that the judgment of the temporal order of two successive stimuli, delivered to the tips of sticks held in each hand, was dramatically altered by crossing the sticks without changing the positions of the hands. This provided evidence for the referral of tactile signals to the tip of a tool in hand. In this study, we examined importance of force feedback from the tool in the referral by manipulating the direction of force feedback in a virtual reality. The virtual tool consisted of a spherical action point that was moved with a stylus in hand. Subjects held two styli, one in each hand, put each action point on each of two buttons in the virtual reality, and were required to judge the order of successive taps, delivered to the two styli. We manipulated the direction of reaction force from each button so that it was congruent or incongruent to the visual configuration of the button. When the arms were uncrossed, judgment primarily depended on whether the action points were crossed or not in the visual space. But when the arms were crossed, judgment critically depended on the direction of force feedback. The results show that tactile signals can be referred to the action point in the virtual reality and that the force feedback becomes a critical factor when the arms are crossed.
当我们用工具触摸某物时，我们会在工具的尖端而非手部感受到触觉。山本和北泽[Yamamoto, S., Kitazawa, S., 2001b. Sensation at the tips of invisible tools. Nat. Neurosci. 4, 979 - 980]此前表明，对分别握在两只手中的棍子尖端施加的两个连续刺激的时间顺序判断，在不改变手部位置的情况下交叉棍子时会发生显著改变。这为触觉信号被转至手中工具的尖端提供了证据。在本研究中，我们通过在虚拟现实中操纵力反馈的方向，研究了来自工具的力反馈在这种转递中的重要性。虚拟工具由一个球形作用点组成，该作用点由手中的触控笔移动。受试者双手各握一支触控笔，将每个作用点放在虚拟现实中的两个按钮上，并被要求判断施加到两支触控笔上的连续敲击的顺序。我们操纵了来自每个按钮的反作用力方向，使其与按钮的视觉配置一致或不一致。当双臂不交叉时，判断主要取决于作用点在视觉空间中是否交叉。但当双臂交叉时，判断关键取决于力反馈的方向。结果表明，触觉信号可以被转至虚拟现实中的作用点，并且当双臂交叉时，力反馈成为一个关键因素。
