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POSTURAL SWAY VARIABILITY IN RELATION TO SUPRA-POSTURAL TASK DIFFICULTY

SAUNDERS, NICHOLE E
http://rave.ohiolink.edu/etdc/view?acc_num=ucin1179521304

Abstract Details

2007, MA, University of Cincinnati, Arts and Sciences : Psychology.
When a person lightly touches an object with the fingertip, postural sway variability has been reliably shown to decrease. Two hypotheses have been proposed to explain why this reduction in sway variability occurs. The first, proposed by Jeka and Lackner (1994, 1995), concludes that sensory information available in light touch, resulting from stimulation of mechanoreceptors in the fingertip and the arm, is utilized to automatically reduce postural sway. The second hypothesis, proposed by Riley, Stoffregen, Grocki, and Turvey (1999), states that postural control is modulated by the demands imposed by the requirements to precisely control touching. The present experiment tested these competing hypotheses by manipulating the performance parameters of a light-touch task. The maximum level of allowable force produced when touching was manipulated. Producing more force presumably results in greater amounts of sensory stimulation, and, according to the sensory hypothesis, should be accompanied by reduced amounts of postural sway. In contrast, the supra-postural task hypothesis predicts the least postural sway in conditions involving the least maximum allowable force, because reducing the maximum allowable force increases the precision demands of the touching task. Forty-eight right-handed participants were randomly assigned to one of three maximum force production groups (0.75 N, 1.5 N, 2.25 N). Each participant completed five trials during which touching was performed as well as five no-touch control trials. Touch force was measured by the mean and SD of force production, measured using a force transducer, and postural sway was operationalized by the standard deviation (SD), local standard deviation (LSD; the average of SDs computed over non-overlapping, 1-second data windows), and path length of the center of pressure (COP) in both the medio-lateral (ML) and anterior-posterior (AP) directions, measured using a Bertec 4060 NC force platform (fingertip force and the COP were sampled at 100 Hz). Postural sway was reduced when participants touched the surface compared to when not touching, as reflected in the measures SDAP, SDML, LSDAP and LSDML, which was consistent with both hypotheses. Consistent with the sensory hypothesis, but contrary to the supra-postural task hypothesis, the greatest reduction in sway between touching and not touching occurred in the 2.25 N condition for SDAP, LSDAP, and LSDML, indicating that touching had the greatest effect in the condition that required the least amount of precision but generated greater fingertip pressure. However, participants in all groups produced less than 0.75 N of force when touching, on average; mean force production across groups, while statistically different, was similar enough to result in tasks that all required a high degree of precision control over touching. Additional experiments that control the range and absolute amounts of force produced when touching are required to determine the relative contributions of sensory and supra-postural task constraints.
Dr. Michael Riley (Advisor)
34 p.
Psychology, Experimental

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Citations

  • SAUNDERS, N. E. (2007). POSTURAL SWAY VARIABILITY IN RELATION TO SUPRA-POSTURAL TASK DIFFICULTY [Master's thesis, University of Cincinnati]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1179521304

    APA Style (7th edition)

  • SAUNDERS, NICHOLE. POSTURAL SWAY VARIABILITY IN RELATION TO SUPRA-POSTURAL TASK DIFFICULTY. 2007. University of Cincinnati, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ucin1179521304.

    MLA Style (8th edition)

  • SAUNDERS, NICHOLE. "POSTURAL SWAY VARIABILITY IN RELATION TO SUPRA-POSTURAL TASK DIFFICULTY." Master's thesis, University of Cincinnati, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1179521304

    Chicago Manual of Style (17th edition)

ucin1179521304
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© 2007, all rights reserved.
This open access ETD is published by University of Cincinnati and OhioLINK.