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Rachel Coats, John Wann; Do elderly people use online visual control when carrying out a reaching task?. Journal of Vision 2009;9(8):1149. doi: 10.1167/9.8.1149.
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© ARVO (1962-2015); The Authors (2016-present)
Young children rely quite heavily on closed-loop visual feedback to complete precise manual tasks. By the time they reach adolescence they can reach accurately using open-loop visual control and do not need to use continual visual feedback on hand position to regulate actions. Less is known about what happens as we reach old age. Two experiments were carried out to examine how elderly people interact with their environment through simple reach-to-grasp tasks. Nine elderly (mean age = 75) and nine young (mean age = 27) participants performed two reaching tasks in which vision of the hand was available on only half the trials. In the first task participants had to pick up one of three target objects by its grasp points (which varied in size). A mirror was used to produce a ‘virtual’ object in the trials when vision of the hand was unavailable. In the second task the set-up remained largely the same, but this time participants had to place a peg in one of three holes in a pegboard.
Mixed ANOVAs revealed that the elderly performed similarly to the young on all aspects of the reach when vision of the hand was available, but when vision was unavailable, compared to the young they seemed to under-reach, take longer to complete the movement, and were less accurate as evidenced by their higher root mean square error scores. Vision of the reaching hand seems to play a vital role as the elderly can perform at similar levels to the young adults when vision of the hand is available, but struggle when they cannot see their hand. Elderly people seem to be processing visual information online when carrying out a reach, and therefore returning to an attention-demanding closed-loop mode of visual control, similar to that used by young children.
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