Periodic change in phase relationship between target and hand motion during visuo-manual tracking task: Behavioral evidence for intermittent control |
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| Affiliation: | 1. Motor Control and Learning Laboratory, Department of Physical Education and Sport Science, Aristotle University of Thessaloniki, Thessaloniki 546 24, Greece;2. Department of Biomechanics, University of Nebraska at Omaha, Omaha, NE, USA;3. Department of Environmental, Agricultural, and Occupational Health, College of Public Health, University of Nebraska Medical Center, Omaha, NE, USA;1. The University of Electro-Communications, Tokyo 182–8585, Japan;2. Tokyo Metropolitan University, Tokyo 191–0065, Japan;3. Japan Aerospace Exploration Agency, Sagamihara 252–5210, Japan;1. Nihon Techno Structure Co., Ltd, Shinyokohama 2-7-17, Kita-ku, Yokohama, Kanagawa, Japan;2. The University of Electro-Communications, Chofugaoka 1-5-1, Chofu, Tokyo, Japan;1. The University of Electro-Communications, Tokyo 182-8585, Japan;2. Tokyo Metropolitan University, Tokyo 191-0065, Japan;3. Japan Aerospace Exploration Agency, Sagamihara 252-5210, Japan;1. Hokkaido University of Science, 7-15-4-1, Maeda, Teine, Sapporo 006-8585, Japan;2. Hokkaido Aerospace Science and Technology Incubation Center, N10W4-301, Kita, Sapporo 001-0010, Japan |
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| Abstract: | When one performs visuo-manual tracking tasks, velocity profile of hand movements shows discontinuous patterns even if the target moves smoothly. A crucial factor of this “intermittency” is considerable delay in the sensorimotor feedback loop, and several researchers have suggested that the cause is intermittent correction of motor commands. However, when and how the brain monitors task performance and updates motor commands in a continuous motor task is uncertain. We examined how tracking error was affected by the timing of target disappearance during a tracking task. Results showed that tracking error, defined as the average phase difference between target and hand, varied periodically in all conditions. Hand preceded target at one specific phase but followed it at another, implying that motor control was not performed in a temporally uniform manner. Tracking stability was evaluated by the variance in phase difference, and changed depending on the timing of target-removal. The variability was larger when target disappeared around turning points than that when it disappeared around the center of motion. This shows that visual information at turning points is more effectively exploited for motor control of sinusoidal target tracking, suggesting that our brain controls hand movements with intermittent reference to visual information. |
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| Keywords: | Motor processes Intermittency Feedback delay Tracking task Feedforward control |
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