Effects of multi-directional vibrotactile feedback on vestibular-deficient postural performance during continuous multi-directional support surface perturbations
Affiliations: [a] Division of Health Sciences and Technology, Harvard-Massachusetts Institute of Technology, Cambridge, MA, USA | [b] Jenks Vestibular Diagnostic Laboratory, Massachusetts Eye and Ear Infirmary, Boston, MA, USA | [c] Department of Otology & Laryngology, Harvard Medical School, Boston, MA, USA | [d] NeuroMuscular Research Center, Boston University, Boston, MA, USA | [e] Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI, USA | [f] Sister Kenny Research Center, Sister Kenny Rehabilitation Institute, Minneapolis, MN, USA
Correspondence:
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Corresponding author: Kathleen Sienko, 2350 Hayward Street, 3116 GG Brown, Ann Arbor, MI 48109-2125, USA. Tel.: +1 734 647 8249; Fax: +1 734 615 6647; E-mail: sienko@umich.edu
Abstract: Single-axis vibrotactile feedback of trunk tilt provided in real-time has previously been shown to significantly reduce the root-mean-square (RMS) trunk sway in subjects with vestibular loss during single-axis perturbation. This research examines the effect of multi-directional vibrotactile feedback on postural sway during continuous multi-directional surface perturbations when the subjects' eyes are closed. Eight subjects with vestibular loss donned a multi-axis feedback device that mapped body tilt estimates onto their torsos with a 3-row by 16-column array of tactile actuators (tactors). Tactor row indicated tilt magnitude and tactor column indicated tilt direction. Root-mean-square trunk tilt, elliptical fits to trunk sway trajectory areas, percentage of time spent outside a no vibrotactile feedback zone, RMS center of pressure, and anchoring index parameters indicating intersegmental coordination were used to assess the efficacy of the multi-directional vibrotactile balance aid. Four tactor display configurations in addition to the tactors off configuration were evaluated. Subjects had significantly reduced RMS trunk sway, significantly smaller elliptical fits of the trajectory area, and spent significantly less time outside of the no feedback zone in the tactors on versus the tactors off configuration. Among the displays evaluated in this study, there was not an optimal tactor column configuration for standing tasks involving continuous surface perturbations. Furthermore, subjects performed worse when erroneous information was displayed. Therefore, a spatial resolution of 90° (4 columns) seems to be as effective as a spatial resolution of 22.5° (16 columns) for control of standing.
