title: The reliance on visual feedback control by older adults is highlighted in tasks requiring precise endpoint placement and precision grip.
abstract: There is an ongoing debate as to whether a greater degree of sensory-motor control is required to maintain skills as humans progress to be septuagenarians. Here, we investigate the dependence of older participants upon vision to execute skilled prehension movements. In a first experiment, participants were required to place a small, round peg in one of three randomly cued holes. A mirror apparatus was used to create conditions where they could always see the target locations, but vision of their hand approaching the target could be removed, and we explored end position accuracy. In a second experiment, we examined the ability of participants to precisely control their grasp action under conditions where they could see the objects but not their hands completing the action. The results showed that in Experiment 1, the older adults undershot the target in their primary submovement and hence had to move further in their secondary movement to achieve their goal. In Experiment 2, the older adults spent longer in the final adjustment phase (a near zero velocity phase at the end of the reach) when vision of the hand was unavailable. These findings suggest that older adults are indeed more reliant on visual feedback than the young in tasks that require precise manual control, and this clarifies conflicting accounts in the prior literature.
authors.affiliation: Department of Psychological and Brain Sciences, Indiana University, 1101 E 10th Street, Bloomington, IN 47405, USA. rcoats@indiana.edu
authors.forename: Rachel O
authors.initials: RO
authors.lastname: Coats
authors.forename: John P
authors.initials: JP
authors.lastname: Wann
mesh_terms: D000328:Adult; D000368:Aged; D000375:Aging / Q000502:physiology*; D000704:Analysis of Variance; D056228:Feedback, Sensory / Q000502:physiology*; D005260:Female; D018737:Hand Strength / Q000502:physiology*; D006801:Humans; D008297:Male; D009068:Movement / Q000502:physiology*; D011597:Psychomotor Performance / Q000502:physiology*; D011930:Reaction Time / Q000502:physiology; D013997:Time Factors; D014785:Vision, Ocular / Q000502:physiology