The contribution of vestibular and proprioceptive information to trunk stabilization varies between postural tasks and walking speeds

Background:Sensory information is integrated based on its reliability to estimate an<br/>internal model of the body in relation to the environment. This integration ensures the<br/>capability to compensate for the loss or interruption of input from one or more sensory modalities. Moreover, reliability and utility of sensory information may depend on the task performed, and consequently the contribution of sensory modalities may vary across postural tasks [1] [2]. In this study, we investigated whether and how the vestibular and proprioceptive information contributes to trunk stabilization in different postural tasks, and in walking at different speeds. <br/><br/>Methods:Healthy adults (n = 12, 20.9 ± 4.1 years) performed a range of tasks in a random order: sitting, standing on the right foot or both feet, and treadmill walking at five speeds: 0.8, 2.0, 3.2, 4.3 and 5.5 km/h. During these tasks, participants were exposed to ten epochs of either a step-like electrical vestibular stimulation (EVS, with the amplitude of 1 mA), or unilateral muscle vibration (MV, 80 Hz) on the right paraspinal muscle at the level of the second lumbar vertebra. Each epoch consisted of 5-seconds stimuli with 10-seconds intervals. Ground reaction forces were recorded to identify the gait events. The averaged mediolateral displacement of the marker at the sixth thoracic level (T6) in the global coordinate was used to evaluate the responses to sensory stimulation. One sample t test compared to 0 was used to evaluate the effect of stimuli. One way ANOVA was used to compare the difference in response across postural tasks and walking speeds. Results:MV induced significant mediolateral displacement of the T6 marker to the left during unipedal standing (p = 0.03), and to the right during bipedal standing (p = 0.03) and sitting (p &lt; 0.01), with a larger effect observed in sitting (p &lt; 0.01). No significant displacement was induced by EVS during unipedal standing (p = 0.33), bipedal standing (p = 0.64), or sitting (p = 0.53). During walking, both EVS and MV induced significant leftward T6 displacement at all walking speeds. The effect of MV (p = 0.03) and EVS (p &lt; 0.01) varied with speeds. The effect of stimuli increased with speed from 0.8 to 3.2 km/h and then decreased at higher speeds for MV, while for EVS, it increased with speeds till 4.3 km/h then decreased at 5.5 km/h.<br/><br/>Conclusions: Responses to vestibular and proprioceptive stimulation vary across postural tasks and walking speeds. The similarity of EVS and MV-induced responses between unipedal standing and walking suggests a similar contribution of these sensory information in stabilization control, which differs from the other postures. The decreased impact of sensory stimuli at higher walking speeds suggests that stablization of faster walking relies less on feedback control. <br/><br/>Reference:<br/>[1] Peterka RJ (2002). J Neurophysiol 88, 1097–1118.<br/>[2] Asslander L., et al. (2016). J Neurophysiol 116, 272–285.