Amputees “Neglect” the Space Near Their Missing Hand

Abstract

The space within reach of our hands is the medium for reaching, grasping, and avoidance movements. Accordingly, visual information in this action space is organized in hand-centered coordinates (Graziano, Yap, & Gross, 1994; Makin, Holmes, Brozzoli, Rossetti, & Farne, 2009; Makin, Holmes, & Zohary, 2007), generating a common frame of reference for perception and action (Fogassi & Luppino, 2005; Graziano, 1999). We hypothesized that amputation of the hand, producing an asymmetry in action space, would cause permanent distortions in visuospatial perception. We hypothesized further that this visual distortion would be limited to near space, because hand actions are not possible in far space. We report here that amputation of a hand is indeed associated with a mild visual neglect of the amputated side: Participants with an amputated hand favored their intact side when comparing distances in a landmarkposition judgment task. Importantly, this bias was absent when the targets were placed in far space. Our results thus demonstrate that the possibility for action within near space shapes the actor’s spatial perception.