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Effects of Cognitive Load on the Amount and Temporal Structure of Postural Sway Variability in Stroke Survivors Publisher Pubmed



Mehdizadeh H1 ; Khalaf K2 ; Ghomashchi H3 ; Taghizadeh G4, 5 ; Ebrahimi I6 ; Taghavi Azar Sharabiani P7 ; Mousavi SJ8 ; Parnianpour M9
Authors
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Authors Affiliations
  1. 1. Department of Neurosciences, School of Advanced Technologies in Medicine, Tehran University of Medical Sciences, Tehran, Iran
  2. 2. Department of Biomedical Engineering, Khalifa University of Science, Technology and Research, Abu Dhabi, United Arab Emirates
  3. 3. Faculty of Mechanical and Industrial Engineering, Islamic Azad University, Qazvin Branch, Qazvin, Iran
  4. 4. Department of Occupational Therapy, Faculty of Rehabilitation Sciences, Iran University of Medical Sciences, Shahnazari Street, Mirdamad Boulevard, Tehran, Iran
  5. 5. Rehabilitation Research Center, Faculty of Rehabilitation Sciences, Iran University of Medical Sciences, Tehran, Iran
  6. 6. Department of Physical Therapy, Faculty of Rehabilitation Sciences, Iran University of Medical Science, Tehran, Iran
  7. 7. Shafa Yahyaian Hospital, Tehran, Iran
  8. 8. Faculty of Health Sciences, University of Sydney, Sydney, Australia
  9. 9. Department of Mechanical Engineering, Sharif University of Technology, Tehran, Iran

Source: Experimental Brain Research Published:2018


Abstract

This study aimed to investigate the variability in postural sway patterns during quiet standing in stroke survivors. The postural sway was measured in 19 stroke survivors, as well as 19 healthy demographically matched participants, at 3 levels of postural difficulty (rigid surface with closed and open eyes, and foam surface with closed eyes), and 3 levels of cognitive difficulty (without a cognitive task, easy and difficult cognitive tasks). Both linear analyses (the amount of postural sway variability, including the standard deviation of the COP velocity in both the anteroposterior (AP) and mediolateral (ML) directions), as well as non-linear analyses [the temporal structure of the COP variability, including % Recurrence, % Determinism, Shannon Entropy, Trend and the maximum diagonal line (Dmax)] were employed. The results revealed that the amount of variability of the postural sway of stroke survivors was significantly greater than that of healthy participants, along both the ML and AP directions, with the highest obtained during standing on foam with closed eyes. All measures of the temporal structure of the COP variability were significantly greater in stroke survivors, as compared to the control group, along the ML direction, but not along the AP direction. The cognitive error was significantly higher during difficult cognitive tasks, although it was neither affected by postural difficulty nor by group. The different results obtained for the amount and temporal structure of the COP variability in the AP and ML directions shed light on the intricate mechanisms employed by the CNS in post-stroke balance control, and suggest that effective rehabilitative and therapeutic strategies should be patient-specific, taking both the environment/surface as well as the specific protocols into consideration. © 2017, Springer-Verlag GmbH Germany, part of Springer Nature.
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