title: Alteration of a motor learning rule under mirror-reversal transformation does not depend on the amplitude of visual error.
abstract: Human's sophisticated motor learning system paradoxically interferes with motor performance when visual information is mirror-reversed (MR), because normal movement error correction further aggravates the error. This error-increasing mechanism makes performing even a simple reaching task difficult, but is overcome by alterations in the error correction rule during the trials. To isolate factors that trigger learners to change the error correction rule, we manipulated the gain of visual angular errors when participants made arm-reaching movements with mirror-reversed visual feedback, and compared the rule alteration timing between groups with normal or reduced gain. Trial-by-trial changes in the visual angular error was tracked to explain the timing of the change in the error correction rule. Under both gain conditions, visual angular errors increased under the MR transformation, and suddenly decreased after 3-5 trials with increase. The increase became degressive at different amplitude between the two groups, nearly proportional to the visual gain. The findings suggest that the alteration of the error-correction rule is not dependent on the amplitude of visual angular errors, and possibly determined by the number of trials over which the errors increased or statistical property of the environment. The current results encourage future intensive studies focusing on the exact rule-change mechanism.
authors.affiliation: Department of Biosciences and Informatics, Faculty of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama, Kanagawa 223-8522, Japan. Electronic address: kasuga@brain.bio.keio.ac.jp.
authors.forename: Shoko
authors.initials: S
authors.lastname: Kasuga
authors.affiliation: Department of Biosciences and Informatics, Faculty of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama, Kanagawa 223-8522, Japan. Electronic address: kurata@brain.bio.keio.ac.jp.
authors.forename: Makiko
authors.initials: M
authors.lastname: Kurata
authors.affiliation: Department of Rehabilitation Medicine, Keio University School of Medicine, 35 Shinanomachi, Shinjuku, Tokyo 160-8582, Japan. Electronic address: meigenliukeio@mac.com.
authors.forename: Meigen
authors.initials: M
authors.lastname: Liu
authors.affiliation: Department of Biosciences and Informatics, Faculty of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama, Kanagawa 223-8522, Japan; Department of Rehabilitation Medicine, Keio University School of Medicine, 35 Shinanomachi, Shinjuku, Tokyo 160-8582, Japan. Electronic address: ushiba@brain.bio.keio.ac.jp.
authors.forename: Junichi
authors.initials: J
authors.lastname: Ushiba
mesh_terms: D000222:Adaptation, Physiological; D000328:Adult; D000704:Analysis of Variance; D056228:Feedback, Sensory; D005260:Female; D006801:Humans; D007858:Learning / Q000502:physiology*; D008297:Male; D009068:Movement / Q000502:physiology*; D010775:Photic Stimulation; D011597:Psychomotor Performance / Q000502:physiology*; D011930:Reaction Time / Q000502:physiology; D014796:Visual Perception / Q000502:physiology*; D055815:Young Adult
keywords: Arm-reaching; Error history; Error sensitivity; Mirror-reversal transformation; Visual gain; Visuomotor learning