title: Different strategy of hand choice after learning of constant and incremental dynamical perturbation in arm reaching.
abstract: In daily life, we encounter situations where we must quickly decide which hand to use for a motor action. Here, we investigated whether the hand chosen for a motor action varied over a short timescale (i.e., hours) with changes in arm dynamics. Participants performed a reaching task in which they moved a specified hand to reach a target on a virtual reality display. During the task, a resistive viscous force field was abruptly applied to only the dominant hand (DH). To evaluate changes in hand choice caused by this perturbation, participants performed an interleaved choice test in which they could freely choose either hand for reaching. Furthermore, to investigate the effect of temporal changes on arm dynamics and hand choice, we exposed the same participants to another condition in which the force field was introduced gradually. When the abrupt force was applied, use of the perturbed hand significantly decreased and not changed during the training. In contrast, when the incremental force was applied, use of the perturbed hand gradually decreased as force increased. Surprisingly, even though the final amount of force was identical between the two conditions, hand choice was significantly biased toward the unperturbed hand in the gradual condition. These results suggest that time-varying changes in arm dynamics may have a greater influence on hand choice than the amplitude of the resistant force itself.
authors.affiliation: Center for Biosciences and Informatics, School of Fundamental Science and Technology, Graduate School of Science and Technology, Keio University Kanagawa, Japan.
authors.forename: Chie
authors.initials: C
authors.lastname: Habagishi
authors.affiliation: Department of Biosciences and Informatics, Faculty of Science and Technology, Keio University Kanagawa, Japan.
authors.forename: Shoko
authors.initials: S
authors.lastname: Kasuga
authors.affiliation: Department of Rehabilitation Medicine, Keio University School of Medicine Tokyo, Japan.
authors.forename: Yohei
authors.initials: Y
authors.lastname: Otaka
authors.affiliation: Department of Rehabilitation Medicine, Keio University School of Medicine Tokyo, Japan.
authors.forename: Meigen
authors.initials: M
authors.lastname: Liu
authors.affiliation: Department of Biosciences and Informatics, Faculty of Science and Technology, Keio University Kanagawa, Japan ; Department of Rehabilitation Medicine, Keio University School of Medicine Tokyo, Japan.
authors.forename: Junichi
authors.initials: J
authors.lastname: Ushiba
keywords: decision making; energy expenditure; force field; hand bias; motor learning