This study investigated the effects of dementia on standing postural adaptation during performance of a visual search task. We recruited 16 older adults with dementia and 15 without dementia. Postural sway was assessed by recording medial-lateral (ML) and anterior-posterior (AP) center-of-pressure when standing with and without a visual search task; i.e., counting target letter frequency within a block of displayed randomized letters. ML sway variability was significantly higher in those with dementia during visual search as compared to those without dementia and compared to both groups during the control condition. AP sway variability was significantly greater in those with dementia as compared to those without dementia, irrespective of task condition. In the ML direction, the absolute and percent change in sway variability between the control condition and visual search (i.e., postural adaptation) was greater in those with dementia as compared to those without. In contrast, postural adaptation to visual search was similar between groups in the AP direction. As compared to those without dementia, those with dementia identified fewer letters on the visual task. In the non-dementia group only, greater increases in postural adaptation in both the ML and AP direction, correlated with lower performance on the visual task. The observed relationship between postural adaptation during the visual search task and visual search task performance-in the non-dementia group only-suggests a critical link between perception and action. Dementia reduces the capacity to perform a visual-based task while standing and thus, appears to disrupt this perception-action synergy.
Bibliographical noteFunding Information:
This manuscript writing of this work was conducted with the support of a National Institutes of Health (NIH)–National Institute on Aging T32 Translational Research in Aging Award (5T32AG023480) and Diversity Supplement Award (3R01AG041785-02S1), unrelated to this project (awarded to A.J.). KL2 Medical Research Investigator Training (MeRIT) award (1KL2RR025757-04) from Harvard Catalyst, unrelated to this project (awarded to B.M.). The preparation of this manuscript was also supported by the Harvard Catalyst. The Harvard Clinical and Translational Science Center (National Center for Research Resources and the National Center for Advancing Translational Sciences, NIH Award UL1 TR001102) and financial contributions from Harvard University and its affiliated academic healthcare centers. The content is solely the responsibility of the authors and does not necessarily represent the official views of Harvard Catalyst, Harvard University and its affiliated academic health care centers, the National Center for Research Resources, or the NIH.
© 2015 Elsevier Ireland Ltd.
- Alzheimer's disease
- Dual task
- Postural adaptation
- Postural sway
- Visual search task