title: Electrical vestibular stimuli to enhance vestibulo-motor output and improve subject comfort.
abstract: Electrical vestibular stimulation is often used to assess vestibulo-motor and postural responses in both clinical and research settings. Stochastic vestibular stimulation (SVS) is a recently established technique with many advantages over its square-wave counterpart; however, the evoked muscle responses remain relatively small. Although the vestibular-evoked responses can be enhanced by increasing the stimulus amplitude, subjects often perceive these higher intensity electrical stimuli as noxious or painful. Here, we developed multisine vestibular stimulation (MVS) signals that include precise frequency contributions to increase signal-to-noise ratios (SNR) of stimulus-evoked muscle and motor responses. Subjects were exposed to three different MVS stimuli to establish that: 1) MVS signals evoke equivalent vestibulo-motor responses compared to SVS while improving subject comfort and reducing experimentation time, 2) stimulus-evoked vestibulo-motor responses are reliably estimated as a linear system and 3) specific components of the cumulant density time domain vestibulo-motor responses can be targeted by controlling the frequency content of the input stimulus. Our results revealed that in comparison to SVS, MVS signals increased the SNR 3-6 times, reduced the minimum experimentation time by 85% and improved subjective measures of comfort by 20-80%. Vestibulo-motor responses measured using both EMG and force were not substantially affected by nonlinear distortions. In addition, by limiting the contribution of high frequencies within the MVS input stimulus, the magnitude of the medium latency time domain motor output response was increased by 58%. These results demonstrate that MVS stimuli can be designed to target and enhance vestibulo-motor output responses while simultaneously improving subject comfort, which should prove beneficial for both research and clinical applications.
authors.affiliation: Department of Biomechanical Engineering, Faculty of Mechanical, Maritime and Materials Engineering, Delft University of Technology, Delft, The Netherlands.
authors.forename: Patrick A
authors.initials: PA
authors.lastname: Forbes
authors.affiliation: School of Kinesiology, University of British Columbia, Vancouver, British Columbia, Canada.
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Dakin
authors.affiliation: Department of Biomechanical Engineering, Faculty of Mechanical, Maritime and Materials Engineering, Delft University of Technology, Delft, The Netherlands.
authors.forename: Anoek M
authors.initials: AM
authors.lastname: Geers
authors.affiliation: Department of Biomechanical Engineering, Faculty of Mechanical, Maritime and Materials Engineering, Delft University of Technology, Delft, The Netherlands.
authors.forename: Martijn P
authors.initials: MP
authors.lastname: Vlaar
authors.affiliation: Department of Biomechanical Engineering, Faculty of Mechanical, Maritime and Materials Engineering, Delft University of Technology, Delft, The Netherlands.
authors.forename: Riender
authors.initials: R
authors.lastname: Happee
authors.affiliation: School of Kinesiology, University of British Columbia, Vancouver, British Columbia, Canada ; MEA Forensic Engineers & Scientists, Richmond, British Columbia, Canada.
authors.forename: Gunter P
authors.initials: GP
authors.lastname: Siegmund
authors.affiliation: Department of Biomechanical Engineering, Faculty of Mechanical, Maritime and Materials Engineering, Delft University of Technology, Delft, The Netherlands ; Laboratory of Biomechanical Engineering, Institute for Biomedical Technology and Technical Medicine (MIRA), University of Twente, Enschede, The Netherlands.
authors.forename: Alfred C
authors.initials: AC
authors.lastname: Schouten
authors.affiliation: School of Kinesiology, University of British Columbia, Vancouver, British Columbia, Canada ; Brain Research Center, University of British Columbia, Vancouver, British Columbia, Canada ; Institute for Computing, Information and Cognitive Systems, University of British Columbia, Vancouver, British Columbia, Canada.
authors.forename: Jean-Sébastien
authors.initials: JS
authors.lastname: Blouin
mesh_terms: D000328:Adult; D004558:Electric Stimulation; D004576:Electromyography; D005071:Evoked Potentials; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D059629:Signal-To-Noise Ratio; D014722:Vestibule, Labyrinth / Q000502:physiology*; D055815:Young Adult