University Joseph Fourier, TIMC-IMAG Laboratory, UMR CNRS 5525, Grenoble F-38706, France.
Neuroscience. 2010 Sep 1;169(3):1199-215. doi: 10.1016/j.neuroscience.2010.05.072. Epub 2010 Jun 4.
The causes of the interindividual differences (IDs) in how we perceive and control spatial orientation are poorly understood. Here, we propose that IDs partly reflect preferred modes of spatial referencing and that these preferences or "styles" are maintained from the level of spatial perception to that of motor control. Two groups of experimental subjects, one with high visual field dependency (FD) and one with marked visual field independency (FI) were identified by the Rod and Frame Test, which identifies relative dependency on a visual frame of reference (VFoR). FD and FI subjects were tasked with standing still in conditions of increasing postural difficulty while visual cues of self-orientation (a visual frame tilted in roll) and self-motion (in stroboscopic illumination) were varied and in darkness to assess visual dependency. Postural stability, overall body orientation and modes of segmental stabilization relative to either external (space) or egocentric (adjacent segments) frames of reference in the roll plane were analysed. We hypothesized that a moderate challenge to balance should enhance subjects' reliance on VFoR, particularly in FD subjects, whereas a substantial challenge should constrain subjects to use a somatic-vestibular based FoR to prevent falling in which case IDs would vanish. The results showed that with increasing difficulty, FD subjects became more unstable and more disoriented shown by larger effects of the tilted visual frame on posture. Furthermore, their preference to coalign body/VFoR coordinate systems lead to greater fixation of the head-trunk articulation and stabilization of the hip in space, whereas the head and trunk remained more stabilized in space with the hip fixed on the leg in FI subjects. These results show that FD subjects have difficulties at identifying and/or adopting a more appropriate FoR based on proprioceptive and vestibular cues to regulate the coalignment of posturo/exocentric FoRs. The FI subjects' resistance in the face of altered VFoR and balance challenge resides in their greater ability to coordinate movement by coaligning body axes with more appropriate FoRs (provided by proprioceptive and vestibular co-variance).
个体间在感知和控制空间方向方面存在差异的原因尚未完全清楚。在这里，我们提出，这些差异部分反映了空间参照的偏好模式，而这些偏好或“风格”从空间感知到运动控制层面都得以维持。通过棒框测试确定了两组实验对象，一组具有较高的视觉场依存性（FD），另一组具有明显的视觉独立性（FI）。FD 和 FI 受试者被要求在增加姿势难度的情况下保持静止，同时改变自我定向的视觉线索（倾斜的视觉框架）和自我运动（频闪照明）以及在黑暗中，以评估视觉依赖性。分析了姿势稳定性、整体身体方向以及在滚动平面中外（空间）或自我（相邻节段）参照框架的节段稳定模式。我们假设，适度的平衡挑战应该会增强受试者对 VFoR 的依赖，尤其是在 FD 受试者中，而较大的挑战应该限制受试者使用基于躯体 - 前庭的 FoR 来防止跌倒，在这种情况下，个体差异将消失。结果表明，随着难度的增加，FD 受试者变得更加不稳定和迷失方向，倾斜的视觉框架对姿势的影响更大。此外，他们将身体/VFoR 坐标系对齐的偏好导致头部 - 躯干关节的固定和髋关节在空间中的稳定，而 FI 受试者中髋关节固定在腿部时头部和躯干在空间中保持更稳定。这些结果表明，FD 受试者在识别和/或采用基于本体感觉和前庭线索的更合适的 FoR 方面存在困难，以调节姿势/外参照 FoR 的对齐。FI 受试者在改变 VFoR 和平衡挑战面前的抵抗力在于他们通过将身体轴与更合适的 FoR（由本体感觉和前庭协方差提供）对齐来协调运动的能力更强。
