• Michihiro Osumi, Masahiko Sumitani, Naoki Wake, Yuko Sano, Akimichi Ichinose, Kumagaya Shin-Ichiro S Research Center for Advanced Science and Technology, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan., Yasuo Kuniyoshi, and Shu Morioka.
• Neurorehabilitation Research Center, Kio University, 4-2-2 Umaminaka, Koryo-cho, Kitakatsuragi-gun, Nara 635-0832, Japan. Electronic address: m.ohsumi@kio.ac.jp.
• Neurosci. Lett. 2015 Sep 25; 605: 7-11.

AbstractThe relation between phantom limb pain (PLP) and the movement representation of a phantom limb remains controversial in several areas of neurorehabilitation, although there are a few studies in which the representation of phantom limb movement was precisely evaluated. We evaluated the structured movement representation of a phantom limb objectively using a bimanual circle-line coordination task. We then investigated the relation between PLP and the structured movement representation. Nine patients with a brachial plexus avulsion injury were enrolled who perceived a phantom limb and had neuropathic pain. While blindfolded, the participants repeatedly drew vertical lines using the intact hand and intended to draw circles using the phantom limb simultaneously. "Drawing of circles" by the phantom limb resulted in an oval transfiguration of the vertical lines ("bimanual coupling" effect). We used an arbitrary ovalization index (OI) to quantify the oval transfiguration. When the OI neared 100%, the trajectory changed toward becoming more circular. A significant negative correlation was observed between the intensity of PLP and the OI (r=-0.66, p<0.05). Our findings directly suggest that structured movement representations of the phantom limb are necessary for alleviating PLP. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

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