Studies of reach control with the body stationary have shown that proprioceptive and visual feedback signals contributing to rapid corrections during reaching are processed by neural circuits that incorporate knowledge about the physical properties of the limb (an "internal model"). However, among the most common spatial and mechanical perturbations to the limb are those caused by our body's own motion, suggesting that processing of vestibular signals for online reach control may reflect a similar level of sophistication. We investigated this hypothesis using galvanic vestibular stimulation (GVS) to selectively activate the vestibular sensors, simulating body rotation, as human subjects reached to remembered targets in different directions (forward, leftward, rightward). If vestibular signals contribute to purely kinematic/spatial corrections for body motion, GVS should evoke reach trajectory deviations of similar size in all directions. In contrast, biomechanical modeling predicts that if vestibular processing for online reach control takes into account knowledge of the physical properties of the limb and the forces applied on it by body motion, then GVS should evoke trajectory deviations that are significantly larger during forward and leftward reaches as compared to rightward reaches. When GVS was applied during reaching, the observed deviations were on average consistent with this prediction. In contrast, when GVS was instead applied before reaching, evoked deviations were similar across directions, as predicted for a purely spatial correction mechanism. These results suggest that vestibular signals, like proprioceptive and visual feedback, are processed for online reach control via sophisticated neural mechanisms that incorporate knowledge of limb biomechanics.

中文翻译：

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通过具有肢体生物力学知识的机制处理对在线到达执行的前庭贡献

对身体静止时的伸展控制的研究表明，有助于在伸展过程中快速纠正的本体感觉和视觉反馈信号是由神经回路处理的，这些神经回路包含有关肢体物理特性的知识（“内部模型”）。然而，最常见的肢体空间和机械扰动是由我们身体自身的运动引起的，这表明用于在线伸展控制的前庭信号处理可能反映了类似的复杂程度。我们使用电流前庭刺激 (GVS) 来研究这一假设，以选择性激活前庭传感器，模拟身体旋转，因为人类受试者在不同方向（向前、向左、向右）到达记住的目标。如果前庭信号有助于对身体运动进行纯粹的运动学/空间校正，则 GVS 应引起所有方向上类似大小的到达轨迹偏差。相比之下，生物力学模型预测，如果在线伸展控制的前庭处理考虑到肢体的物理特性和身体运动施加在其上的力的知识，那么 GVS 应该引起在向前和向左伸展过程中明显更大的轨迹偏差与向右到达相比。在到达期间应用 GVS 时，观察到的偏差平均与该预测一致。相比之下，当在到达之前应用 GVS 时，诱发偏差在各个方向上是相似的，正如纯空间校正机制所预测的那样。这些结果表明前庭信号，