Assessment of verticality perception is increasingly used in patients with disorders of upright body orientation, e.g. in pusher behavior after hemispheric stroke or in retropulsion in neurovascular or degenerative diseases. The subjective postural vertical (SPV) assesses the individual's perceived upright body orientation in space and can be determined in a sitting or a standing position. As somatosensory input differs between sitting and standing, we suppose a different representation of verticality. Thus, the aim of this study was to compare the SPV while sitting and while standing, and to determine the influence of proprioceptive and visual stimulations on the SPV in both positions. Twenty healthy subjects (18-40 years, 9 female) participated in two experiments. In experiment 1 the SPV was assessed in the pitch and roll planes while sitting and standing. In experiment 2 we additionally applied somatosensory Achilles tendon vibration and visual optokinetic stimulation. Results of experiment 1 revealed no difference of the SPV error between sitting and standing. Though, we found an increased SPV variability while sitting. Experiment 2 showed no effect of sensory manipulation in the pitch plane, but an effect of optokinetic stimulation in the roll plane. The tilt in direction of the visual stimuli was more pronounced while sitting. Optokinetic stimulation also resulted in a larger SPV variability in roll, indicating larger insecurity in verticality estimation during stimulation. In conclusion, even though the SPV assessment while sitting and standing resulted in similar mean values, the larger variability and the higher sensitivity to visual stimuli while sitting suggest different strategies for verticality estimation while sitting and while standing.

中文翻译：

---

在健康受试者中坐着和站立时，姿势和姿势在滚动和俯仰中的感觉。

垂直感知的评估越来越多地用于具有直立身体定向障碍的患者，例如，在半球卒中后的推动行为或在神经血管或退行性疾病中的反冲。主观姿势垂直（SPV）可以评估个人在空间中感觉到的直立身体方位，并且可以在坐着或站立时确定。由于坐和站之间的体感输入不同，我们假设垂直度的表示形式有所不同。因此，本研究的目的是比较坐立和站立时的SPV，并确定本体感受性和视觉刺激对两个位置中SPV的影响。20名健康受试者（18-40岁，女性9名）参加了两个实验。在实验1中，坐着和站着时在俯仰和侧倾平面上评估了SPV。在实验2中，我们还应用了体感跟腱振动和视觉光动力刺激。实验1的结果表明，坐和站之间SPV误差没有差异。不过，我们发现坐着时SPV的变异性增加了。实验2显示在俯仰平面上没有感觉操纵的作用，但是在侧倾平面上有视动刺激的作用。坐着时视觉刺激方向的倾斜更明显。光动力学刺激还导致侧倾中较大的SPV变异性，表明刺激期间垂直度估计中的较大不安全性。总之，即使坐下和站立时的SPV评估得出相似的平均值，