Human Physiology Theses and Dissertations

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Browsing Human Physiology Theses and Dissertations by Subject "Automatic Postural Response"

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    The Role of Attention in Fall Avoidance: Evaluation of Dual Task Interference with Postural and Visual Working Memory Tasks in Young Versus Older Adults, Does Capacity Limitation Influence Postural Responses?
    (University of Oregon, 2013-07-11) Little, Carrie; Woollacott, Marjorie
    The primary goal of this research was to explore attentional factors contributing to normal balance control and to determine how age-related changes in these factors constrain balance in the aging adult. Though previous research has demonstrated attentional interference between postural control and performance of cognitive tasks in young (YA) and older adults (OA), the mechanisms contributing to interference have not been identified. This study utilized as a cognitive task, a visual working memory task (the change detection task), which identified the short term working memory (or attentional) capacity limits of participants. Participants were asked to perform the cognitive task (determining a change in the color of squares in a first vs. second memory array) either in isolation or with postural tasks of increasing complexity, including quiet sitting (control), quiet stance in isolation, quiet stance (but intermixed with support surface perturbations), and support surface perturbations. YA showed a significant decline in working memory capacity between the control and perturbation condition (p<0.01) but no change in postural performance between single and dual task conditions, as determined by increased steps in response to perturbations (p<0.33). In a second set of experiments, the performance of OA was compared to YA. Results showed that OA had reduced working memory capacity on the change detection task compared to YA even in the control condition (YA: 2.8±0.6 items; OA: 1.8±0.7; p<0.001). OA showed an even greater decline than YA in memory capacity in the dual task condition (p<0.001), along with difficulty regaining balance following perturbations, evidenced by significant increases in up on toes (p<0.05) and stepping strategies (p<0.05). These results suggest that visual working memory (for simple features) and postural control share a common attentional resource that is limited and that postural control is favored over the cognitive task in YA. In OA, attentional capacity was significantly reduced and both postural and cognitive tasks were impaired in the dual task condition, suggesting that with aging even simple cognitive tasks can negatively affect balance under challenging postural conditions.