• Tomoyo Morita, Minoru Asada, and Eiichi Naito.
• Institute for Open and Transdisciplinary Research Initiatives, Osaka University, 1-1 Yamadaoka, Suita, Osaka 565-0871, Japan; Center for Information and Neural Networks (CiNet), National Institute of Information and Communications Technology (NICT), 2A6 1-4 Yamadaoka, Suita, Osaka 565-0871, Japan. Electronic address: morita@otri.osaka-u.ac.jp.
• Neuroscience. 2020 Jan 15; 425: 68-89.

AbstractVisual self-face and proprioceptive postural recognition predominantly activate the right inferior frontoparietal cortices in human right-handers at the population level. In the present study, prompted by the finding that left-handedness may alter lateralized cortical organization for language, sensory-motor, and cognitive functions observed in right-handers, we investigated individual variations in right-dominant use of the cortices in 50 right-handers and 50 left-handers during self-body recognition (self-face and proprioceptive) tasks. We also investigated possible between-tasks differences in this right-dominant use, and possible atypical left-right reversed lateralization (right-dominance for language and left-dominance for self-body recognition) in left-handers. We measured brain activity using functional magnetic resonance imaging while participants performed a proprioceptive postural recognition task (experiencing illusory movements of the left and the right hands), a visual self-face recognition (self-other distinction) task, and a language (verb generation) task. To evaluate hemispheric dominance, we computed individual lateralization indices for the inferior frontoparietal activities in these tasks. Left-handedness altered the right-hemispheric dominance that was observed in the majority of right-handed participants in both self-body recognition tasks. In the left-handed group, during proprioceptive recognition, participants with right-lateralization, bilaterality, or left-lateralization were equally distributed, and during self-face recognition, right-lateralization was still observed, though the number of participants who demonstrated left-lateralization increased. Atypical left-right reversed lateralization was only observed in left-handed participants, but during both self-body recognition tasks. The present study provides novel and valuable knowledge about right-hemispheric dominance in self-body recognition affected by left-handedness. We discuss how functional lateralization of self-body recognition is shaped in human brain, in terms of handedness, language lateralization, and development.Copyright © 2019 The Author(s). Published by Elsevier Ltd.. All rights reserved.

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