Experimental Brain Research

, Volume 236, Issue 1, pp 285–296 | Cite as

Effects of cognitive load on the amount and temporal structure of postural sway variability in stroke survivors

  • Hajar Mehdizadeh
  • Kinda Khalaf
  • Hamed Ghomashchi
  • Ghorban TaghizadehEmail author
  • Ismaeil Ebrahimi
  • Parvaneh Taghavi Azar Sharabiani
  • Seyed Javad Mousavi
  • Mohamad Parnianpour
Research Article


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 (D max)] 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.


Stroke Postural control Cognitive load Temporal structure of postural sway 



This study was supported by Iran University of Medical Sciences, Tehran, Iran.

Compliance with ethical standards

Conflict of interest

The authors declare that they have no conflict of interest.


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Copyright information

© Springer-Verlag GmbH Germany, part of Springer Nature 2017

Authors and Affiliations

  • Hajar Mehdizadeh
    • 1
  • Kinda Khalaf
    • 2
  • Hamed Ghomashchi
    • 3
  • Ghorban Taghizadeh
    • 4
    • 5
    Email author
  • Ismaeil Ebrahimi
    • 6
  • Parvaneh Taghavi Azar Sharabiani
    • 7
  • Seyed Javad Mousavi
    • 8
  • Mohamad Parnianpour
    • 9
  1. 1.Department of Neurosciences, School of Advanced Technologies in MedicineTehran University of Medical SciencesTehranIran
  2. 2.Department of Biomedical EngineeringKhalifa University of Science, Technology and ResearchAbu DhabiUAE
  3. 3.Faculty of Mechanical and Industrial EngineeringIslamic Azad UniversityQazvinIran
  4. 4.Department of Occupational Therapy, Faculty of Rehabilitation SciencesIran University of Medical SciencesTehranIran
  5. 5.Rehabilitation Research Center, Faculty of Rehabilitation SciencesIran University of Medical SciencesTehranIran
  6. 6.Department of Physical Therapy, Faculty of Rehabilitation SciencesIran University of Medical ScienceTehranIran
  7. 7.Shafa Yahyaian HospitalTehranIran
  8. 8.Faculty of Health SciencesUniversity of SydneySydneyAustralia
  9. 9.Department of Mechanical EngineeringSharif University of TechnologyTehranIran

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