Differential effects of vision upon the accuracy and precision of vestibular-evoked balance responses

Stuart Mackenzie, Raymond Reynolds

Research output: Contribution to journalArticlepeer-review

3 Citations (Scopus)
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Vestibular information must be transformed from head-to-foot centred coordinates for balance control. This transformation process has previously been investigated using Electrical Vestibular Stimulation (EVS), which evokes a sway response fixed in head coordinates. The craniocentric nature of the response has been demonstrated by analysing average responses to multiple stimuli. This approach misses any trial-by-trial variability which would reflect poor balance control. Here we performed single-trial analysis to measure this directional variability (precision), and compared this to mean performance (accuracy). We determined the effect of vision upon both parameters. Standing volunteers adopted various head orientations (0, ±30 & ±60 deg yaw) while EVS-evoked response direction was determined from ground reaction force vectors. As previously reported, mean force direction was oriented towards the anodal ear, and rotated in line with head yaw. Although vision caused a ~50% reduction in response magnitude, it had no influence upon the direction of the mean sway response, indicating that accuracy was unaffected. However, individual trial analysis revealed up to 30% increases in directional variability with the eyes open. This increase was inversely correlated with the size of the force response. The paradoxical observation that vision reduces the precision of the balance response may be explained by a multi-sensory integration process. As additional veridical sensory information becomes available, this lessens the relative contribution of vestibular input, causing a simultaneous reduction in both the magnitude and precision of the response to EVS. Our novel approach demonstrates the importance of single trial analysis in revealing the efficacy of vestibular reflexes.
Original languageEnglish
JournalThe Journal of Physiology
Early online date16 Apr 2018
Publication statusE-pub ahead of print - 16 Apr 2018


  • balance
  • vestibular-motor transformation
  • accuracy
  • precision


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