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Kazumichi Matsumiya; Eye–hand coordination reveals the role of body awareness in motor control. Journal of Vision 2021;21(9):2279. doi: https://doi.org/10.1167/jov.21.9.2279.
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© ARVO (1962-2015); The Authors (2016-present)
Awareness of the body includes awareness of visible body parts as one’s own (sense of body ownership) and awareness of voluntary actions over those visible body parts (sense of agency). How these senses affect motor control remains unclear. To address this issue, the present study combined the moving rubber hand illusion, which allows experimental manipulation of agency and body ownership over an artificial hand, with the finger-tracking paradigm, which allows behavioral quantification of motor control by the ability of eye–hand coordination. Eye–hand coordination requires awareness of the hand to track the hand with the eyes. In this study, participants tracked a finger of a moving artificial hand with their eyes while the artificial hand moved together with the participant’s hidden hand. The present results show that eye–hand coordination is improved when participants experience a sense of agency over the tracked artificial hand, regardless of their sense of body ownership. Moreover, the eye latency (defined by eye onset time relative to hand onset time) significantly correlated with the strength of sense of agency, but the pursuit gain and number of saccades did not. Eye latency is an indicator of how fast the onset of hand movements evokes pursuit eye movements in the initiation of eye–hand coordination. Pursuit gain and number of saccades are indicators of how precisely pursuit eye movements track hand movements during the maintenance of eye–hand coordination. Thus, the present findings indicate that the improvement by sense of agency is selective for the initiation, but not maintenance, of eye–hand coordination. This suggests that the experience of explicit sense of agency over one's body parts improves the initiation of voluntary motor actions, implying that artificial manipulation of agency may be beneficial to rehabilitation and sports training techniques.
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