Upweighting lumbar proprioception through prolonged electrical vestibular stimulation: an application of sensory reweighting

Postural control relies on multisensory information, which is integrated based on the<br/>relative reliability of the sources, in a process known as ‘sensory reweighting’. Lowback pain (LBP) reduces the lumbar proprioceptive contribution to postural control. As<br/>such, LBP patients may increase dependence on other modalities, such as vestibular<br/>signals. Attenuated response to prolonged electrical vestibular stimulation (EVS),<br/>which induces illusions of self-movement, has been reported. This could temporally<br/>up-weight the lumbar proprioception. Here, we investigated reweighting between<br/>vestibular information and lumbar proprioception during sitting in healthy participants.<br/>Ten participants sat upright on a stool placed on a force plate, with their hands hanging<br/>freely at the sides and their feet on the ground with a 90-degree knee flexion. Trunk<br/>kinematics were measured with markers on the back at the T6 level. Unilateral muscle<br/>vibration (80 Hz) on the left paraspinal muscle at the L2 level was applied, with each<br/>vibration round consisting of ten times 5-second vibrations with 10-second rest<br/>intervals. Vibrations were applied at 0 (MV1), 10 (MV2) and 20 (MV3) minutes during<br/>EVS, and 5 minutes before (Pre-MV) and after EVS (Post-MV). Stochastic EVS (2 to<br/>25 Hz) was applied for entire 30 minutes. The weight of the vestibular signal was<br/>quantified as the gain between EVS and horizontal ground reaction force (GRF) in the<br/>medio-lateral direction. Although the EVS-GRF gain showed no decrease over 30<br/>mintues, trunk roll in Post-MV (0.28 ± 0.17 degrees) increased compared to Pre-MV<br/>(0.25 ± 0.17 degrees, p = 0.15). The presence of EVS significantly increased trunk roll<br/>(Pre-MV vs MV3, p = 0.04). In sum, prolonged EVS temporarily up-weights the lumbar<br/>proprioception in healthy participants. However no post-stimulation effect was found<br/>after 5 minutes of rest. These findings suggest that prolonged EVS could potentially<br/>be applied in the treatment for LBP.