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  • Writer's pictureIan Pennekamp

Research paper: "How prism adaptation reveals the distinct use of size and positions in grasping."


Jeroen B. J. Smeets1 · Ian Pennekamp1 · Bente van Amsterdam1 · Willemijn D. Schot2

Received: 9 September 2022 / Accepted: 7 November 2022 / Published online: 12 November 2022

© The Author(s) 2022


Abstract

The size of an object equals the distance between the positions of its opposite edges. However, human sensory processing for perceiving positions differs from that for perceiving size. Which of these two information sources is used to control grip aperture? In this paper, we answer this question by prism adaptation of single-digit movements of the index finger and

thumb. We previously showed that it is possible to adapt the index finger and thumb in opposite directions and that this adaptation induces an aftereffect in grip aperture in grasping. This finding suggests that grasping is based on the perceived positions of the contact points. However, it might be compatible with grasping being controlled based on size provided

that the opposing prism adaptation leads to changes in visually perceived size or proprioception of hand opening. In that case, one would predict a similar aftereffect in manually indicating the perceived size. In contrast, if grasping is controlled

based on information about the positions of the edges, the aftereffect in grasping is due to altered position information, so one would predict no aftereffect in manually indicating the perceived size. Our present experiment shows that there was no aftereffect in manually indicating perceived size. We conclude that grip aperture during grasping is based on perceived positions rather than on perceived size.


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Keywords Sensorimotor adaptation . Prehension . Inconsistent perception . Goal-directed movement



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