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Rachel Coats, John Wann; Older adults use a distinctive form of visual control to guide bimanual reaches. Journal of Vision 2010;10(7):1097. https://doi.org/10.1167/10.7.1097.
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Background: Previous research has shown that young adults are skilled at coordinating the left and right hands when reaching to grasp two separate objects at the same time, or when carrying two objects to the same location. Less is known about the behaviour of older adults with regard to such tasks. We examined the performance differences between young adults (mean age 20) and older adults (mean age 74) in terms of how they coordinate the two hands during a bimanual movement. Methods: Identical objects were located to the left and right of 3 trays laid out in front of the participants along the fronto-parallel plane. Participants picked up the objects (one in each hand) and placed them in the specified tray simultaneously. Movements of the objects were recorded using a VICON 3D motion capture system. Results: Although no group differences were found in overall movement time, the details of the reach movements were not the same. The older adults moved as quickly as possible to the tray vicinity, producing reaches with greater peak velocities than the young. They then spent longer than the young in the ‘near-zero velocity’ final phase of the reach and made more adjustments during this phase. In contrast, the young spent longer in the preceding low velocity phase than the older adults, and made more adjustments during this phase. Conclusions: We propose that, in contrast to the younger group, older adults have more problems using online sensory feedback to correct trajectory errors during the flight phase. As a result they wait until both hands are together so they can visually monitor both objects before making trajectory corrections.
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