Goar Megan H, Barnett-Cowan Michael, Horslen Brian C
Department of Kinesiology and Health Sciences, University of Waterloo, Waterloo, Ontario, Canada.
J Neurophysiol. 2025 Jan 1;133(1):142-161. doi: 10.1152/jn.00166.2024. Epub 2024 Dec 3.
Integrated multisensory feedback plays a crucial role in balance control. Minimal fingertip contact with a surface (light touch), reduces the center of pressure (CoP) by adding sensory information about postural orientation and balance state. Electrical vestibular stimulation (EVS) can increase sway by adding erroneous vestibular cues. This juxtaposition of conflicting sensory cues can be exploited to explore the dynamics of sensorimotor adaptations. We used continuous stochastic EVS (0-25 Hz; ±4 mA; 200-300 s) to evoke balance responses in CoP (, ). Systems analyses (coherence, gain) quantified coupling and size of balance responses to EVS. We had participants either touch (TOUCH; <2 N) or not touch (NO-TOUCH) a load cell during EVS (, ), or we intermittently removed the touch surface () to measure the effects of light touch on vestibular-evoked balance responses. We hypothesized that coherence and gain between EVS and CoP would decrease, consistent with the central nervous system (CNS) down-weighting vestibular cues that conflict with light touch. Light touch reduced CoP displacement but increased variation in the CoP signal explained by EVS input. Significant coherence between EVS and CoP was observed up to ∼30 Hz in both conditions but was significantly greater in the TOUCH condition from 12 to 28.5 Hz. Conversely, EVS-CoP gain was 63% lower in TOUCH compared with NO-TOUCH. Our findings show that light touch can reduce the size of vestibular-evoked responses but also increase high-frequency vestibular contributions for sway. This suggests that the CNS can use discrete changes in sensory inputs to alter balance behavior but cannot fully suppress responses to a potent cue. This study reveals that minimal fingertip contact (light touch) during balance tasks not only diminishes the impact of electrical vestibular stimulation (EVS) on sway but also exposes a high-frequency center of pressure element, correlated to vestibular inputs, not typically seen in free standing. Specifically, light touch decreases the magnitude of EVS-induced sway while increasing coherence with EVS at higher frequencies. This illustrates the central nervous system's capacity to adaptively reweight sensorimotor processes for balance control.
综合多感官反馈在平衡控制中起着至关重要的作用。与表面进行最小程度的指尖接触（轻触），通过添加有关姿势方向和平衡状态的感觉信息来降低压力中心（CoP）。电前庭刺激（EVS）可通过添加错误的前庭线索来增加摇摆。这种相互矛盾的感觉线索的并置可用于探索感觉运动适应的动态过程。我们使用连续随机EVS（0 - 25Hz；±4mA；200 - 300s）来诱发CoP中的平衡反应（，）。系统分析（相干性、增益）量化了对EVS的平衡反应的耦合和大小。在EVS期间，我们让参与者触摸（TOUCH；<2N）或不触摸（NO - TOUCH）一个测力传感器（，），或者我们间歇性地移除触摸表面（）以测量轻触对前庭诱发的平衡反应的影响。我们假设EVS和CoP之间的相干性和增益会降低，这与中枢神经系统（CNS）降低与轻触冲突的前庭线索的权重一致。轻触减少了CoP位移，但增加了由EVS输入解释的CoP信号的变化。在两种情况下，高达约30Hz时都观察到EVS和CoP之间有显著的相干性，但在12至28.5Hz时，TOUCH条件下的相干性明显更大。相反，与NO - TOUCH相比，TOUCH条件下的EVS - CoP增益低63%。我们的研究结果表明，轻触可以减小前庭诱发反应的大小，但也会增加摇摆的高频前庭贡献。这表明中枢神经系统可以利用感觉输入的离散变化来改变平衡行为，但不能完全抑制对有效线索的反应。这项研究表明，在平衡任务期间最小程度的指尖接触（轻触）不仅会减少电前庭刺激（EVS）对摇摆的影响，还会揭示一个与前庭输入相关的高频压力中心元素，这在自由站立时通常看不到。具体而言，轻触会降低EVS诱发的摇摆幅度，同时在更高频率下增加与EVS的相干性。这说明了中枢神经系统自适应地重新加权感觉运动过程以进行平衡控制的能力。
