The effect of prosthetic feedback on the strategies and synergies used by vestibular loss subjects to control stance

Abstract

BackgroundThis study investigated changes in stance movement strategies and muscle synergies when bilateral peripheral vestibular loss (BVL) subjects are provided feedback of pelvis sway angle.MethodsSix BVL (all male) and 7 age-matched male healthy control (HC) subjects performed 3 stance tasks: standing feet hip width apart, eyes closed, on a firm and foam surface, and eyes open on foam. Pelvis and upper trunk movements were recorded in the roll and pitch planes. Surface EMG was recorded from pairs of antagonistic muscles at the lower leg, trunk and upper arm. Subjects were first assessed without feedback. Then, they received training with vibrotactile, auditory, and fall-warning visual feedback during stance tasks before being reassessed with feedback.ResultsFeedback reduced pelvis sway angle displacements to values of HCs for all tasks. Movement strategies were reduced in amplitude but not otherwise changed by feedback. These strategies were not different from those of HCs before or after use of feedback. Low frequency motion was in-phase and high frequency motion anti-phasic. Feedback reduced amplitudes of EMG, activity ratios (synergies) of antagonistic muscle pairs and slightly reduced baseline muscle activity.ConclusionsThis is the first study demonstrating how vestibular loss subjects achieve a reduction of sway during stance with prosthetic feedback. Unchanged movement strategies with reduced amplitudes are achieved with improved antagonistic muscle synergies. This study suggests that both body movement and muscle measures could be explored when choosing feedback variables, feedback location, and patient groups for prosthetic devices which reduce sway of those with a tendency to fall.

The vestibular implant: A probe in orbit around the human balance system

“…Physical therapy showed no [68] or limited benefit [18]. Other treatment options such as sensory substitution with auditory or vibrotactile feedback have shown contrasting results and are still under clinical investigation [30,32,43]. Recent spectacular results showing the successful differentiation of stem cells into functional hair-cell-like cells and auditory neurons that are similar with the vestibular neurosensory cells, allow the wildest hope for the future [9].…”

Volume of Convex Hull: A Technique for Quantifying Human Postural Stability

“…However, this approach was chosen due to several patients' significant stability problems and their inability to perform multiple tests with CE, as is common in such patients. 23,[40][41][42] Also, use of our results in clinical practice might be limited due to the used measurement conditions in the study (standing on a FiS, etc.). Nevertheless, the authors tried to follow the standard and most commonly used measurement methodology to study postural stability using traditional methods.…”

Trajectory length of pitch vs. roll: Technique for assessment of postural stability

“…A second limitation in this study is that only one measurement of each subject was made. However, measurement of a subject with impaired postural stability is usually done only once, or only data from the trial with the most complete and longest record are used for further analysis (Honegger, Hillebrandt, Elzen, Tang, & Allum, 2013;Horlings, Carpenter, Honegger, & Allum, 2009). This approach was used because some patients had significant stability problems and were unable to perform multiple tests with EC, as is common in these patients (Čakrt et al, 2012).…”