• Marie Chancel, Anne Kavounoudias, and Michel Guerraz.
• Univ. Grenoble Alpes, CNRS, LPNC, F-38000 Grenoble, France; Aix-Marseille University, CNRS, NIA UMR 7260, F-13331 Marseille, France.
• Neuroscience. 2017 Oct 24; 362: 118-126.

AbstractRecent data suggest that manipulating the muscle afferents of one arm affects both ipsilateral and contralateral perceptual estimates. Here, we used the mirror paradigm to study the bimanual integration of kinesthetic muscle afferents. The reflection of a moving hand in a mirror positioned in the sagittal plane creates an illusion of symmetrical bimanual movement. Although vision clearly has a role in kinesthesia, its role in the mirror illusion might have been overestimated. Conversely, the role of bimanual integration of muscle afferents might have been underestimated. We hypothesized that muscle-proprioceptive afferents of the passively displaced arm (the image of which was reflected in the mirror) are involved in this illusion. We evoked in 19 healthy adult participants the mirror illusion by displacing passively their left arm, the image of which was reflected in the mirror. Once participants experienced the illusion that their hidden right arm was moving, we then either occluded their view of the mirror (using occlusive glasses) and/or prevent the passive left arm displacement. Participants' illusion characteristics (duration and kinematic) under these conditions were compared with classical mirror illusion (without visual occlusion). We found that as long as the arm was still moving, the kinesthetic illusion decayed slowly after visual occlusion. These findings suggest that the mirror illusion results from the combination of visuo-proprioceptive signals from the two arms and is not purely visual in origin. Our findings also support the more general concept whereby proprioceptive afferents are integrated bilaterally for the purpose of kinesthesia during bimanual tasks.Copyright © 2017 IBRO. Published by Elsevier Ltd. All rights reserved.

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