Accurate perception of gravity and translation is fundamental for balance, navigation, motor control, etc.. Previous studies have reported that perceptual thresholds for earth-vertical (i.e. parallel to gravity) and earth-horizontal (i.e. perpendicular to gravity) translations are equivalent in healthy adults, suggesting that the nervous system compensates for the presence of gravity. However, past study designs were not able to fully separate the effect of gravity from the potential effects of motion direction and body orientation. To quantify the effect of gravity on translation perception relative to these alternative factors, we measured vestibular perceptual thresholds for three motion directions (inter-aural, naso-occipital, superior-inferior) and three body orientations (upright, supine, ear-down). In contrast to prior reports, our data suggest that the nervous system does not universally compensate for the effects of gravity during translation, instead, we showed that the co-linear effect of gravity significantly decreases the sensitivity to stimuli and this effect was larger for motions sensed by the utricles (inter-aural and naso-occipital translation) than for the saccules (superior-inferior translations). We also identified increased thresholds for superior-inferior translation, suggesting decreased sensitivity of motions sensed predominantly by the saccule, and an overall effect of body orientation on perception; however, post-hoc analyses suggest that this orientation effect may capture the impact of gravity on self-motion perception. Overall, our data provide fundamental insights into the manner by which the nervous system processes vestibular self-motion cues - showing that the effect of gravity on translation perception is impacted by the direction of motion.

中文翻译：

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重力对线性运动感知的影响


对重力和平移的准确感知是平衡、导航、运动控制等的基础。之前的研究报道，地球垂直（即平行于重力）和地球水平（即垂直于重力）平移的感知阈值在健康成年人，表明神经系统补偿了重力的存在。然而，过去的研究设计无法将重力的影响与运动方向和身体方向的潜在影响完全分开。为了量化相对于这些替代因素的重力对平移知觉的影响，我们测量了三个运动方向（耳间、鼻枕、上下）和三个身体方向（直立、仰卧、耳垂）的前庭知觉阈值。与之前的报告相比，我们的数据表明神经系统并不能普遍补偿平移过程中重力的影响，相反，我们表明重力的共线效应显着降低了对刺激的敏感性，并且这种效应对于运动更大椭圆囊（耳间和鼻枕翻译）感知的声音高于球囊（上下翻译）感知的声音。我们还发现上下翻译的阈值增加，这表明主要由球囊感知的运动的敏感性降低，以及身体方向对感知的总体影响；然而，事后分析表明，这种定向效应可能反映了重力对自我运动感知的影响。 总的来说，我们的数据为神经系统处理前庭自我运动线索的方式提供了基本的见解——表明重力对平移感知的影响受到运动方向的影响。