Differential effects of vision upon the accuracy and precision of vestibular-evoked balance responses.
Differential effects of vision upon the accuracy and precision of vestibular-evoked balance responses.
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DOI：
10.1113/jp275645
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发表时间：
2018-06
期刊：
影响因子：
--
通讯作者：
Reynolds RF
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文献类型：
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作者：
Mackenzie SW;Reynolds RF
有效的平衡控制需要前庭信号从头部到脚中心坐标的转换，以便在适当的方向上移动身体。这种转换过程之前已经通过分析对多个前庭电刺激（EVS）的平均摇摆响应的方向精度进行了研究。在这里，我们研究了EVS响应的逐次变异，以测量方向精度的任何变化，这些变化可能被平均过程所掩盖。我们发现视觉在不影响平均摇摆方向的情况下增加了方向可变性，这表明响应精度和精度是可分离的。这些结果强调了单试验分析在确定前庭平衡控制功效方面的重要性。为了平衡控制，前庭信息必须从头中心坐标转换为脚中心坐标。这种转变过程之前已经用前庭电刺激（EVS）进行了研究，它唤起了固定在头部坐标上的摇摆响应。通过分析对多种刺激的平均反应，已经证明了这种反应的脑中心性质。这种方法忽略了任何试验间的可变性，这可能反映出较差的平衡控制。在这里，我们进行了单试验分析来测量这种方向性变化（精度），并将其与平均性能（精度）进行比较。我们确定了视觉对这两个参数的影响。站立志愿者采用不同的头部方向（0、±30和±60°偏角），EVS诱发的反应方向由地面反作用力矢量确定。如前所述，平均力方向朝向阳极耳，并随头部偏航旋转。虽然视觉导致响应幅度降低了50%，但它对平均摇摆响应的方向没有影响，这表明准确性不受影响。然而，个体试验分析显示，睁眼时方向变异性增加30%。这种增加与力响应的大小成反比。视觉降低平衡反应的精确度这一矛盾的观察结果可以用多感觉整合过程来解释。随着额外的感官信息变得可用，前庭输入的相对贡献减少，导致EVS响应的幅度和精度同时降低。我们的新方法证明了单试验分析在揭示前庭反射功效方面的重要性。有效的平衡控制需要前庭信号从头部到脚中心坐标的转换，以便在适当的方向上移动身体。这种转换过程之前已经通过分析对多个前庭电刺激（EVS）的平均摇摆响应的方向精度进行了研究。在这里，我们研究了EVS响应的逐次变异，以测量方向精度的任何变化，这些变化可能被平均过程所掩盖。我们发现视觉在不影响平均摇摆方向的情况下增加了方向可变性，这表明响应精度和精度是可分离的。这些结果强调了单试验分析在确定前庭平衡控制功效方面的重要性。
Effective balance control requires the transformation of vestibular signals from head‐ to foot‐centred coordinates in order to move the body in an appropriate direction. This transformation process has previously been studied by analysing the directional accuracy of the averaged sway response to multiple electrical vestibular stimuli (EVS). Here we studied trial‐by‐trial variability of EVS responses to measure any changes in directional precision which may be masked by the averaging process. We found that vision increased directional variability without influencing the mean sway direction, demonstrating that response accuracy and precision are dissociable. These results emphasise the importance of single trial analysis in determining the efficacy of vestibular control of balance. 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 and ±60 deg yaw) while EVS‐evoked response direction was determined from ground reaction force vectors. As previously reported, mean force direction was orientated towards the anodal ear, and rotated in line with head yaw. Although vision caused a ∼50% reduction in response magnitude, it had no influence on 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 the precision of the response to EVS. Our novel approach demonstrates the importance of single‐trial analysis in revealing the efficacy of vestibular reflexes. Effective balance control requires the transformation of vestibular signals from head‐ to foot‐centred coordinates in order to move the body in an appropriate direction. This transformation process has previously been studied by analysing the directional accuracy of the averaged sway response to multiple electrical vestibular stimuli (EVS). Here we studied trial‐by‐trial variability of EVS responses to measure any changes in directional precision which may be masked by the averaging process. We found that vision increased directional variability without influencing the mean sway direction, demonstrating that response accuracy and precision are dissociable. These results emphasise the importance of single trial analysis in determining the efficacy of vestibular control of balance.