Vingerhoets R A A, Medendorp W P, Van Gisbergen J A M
Department of Biophysics, Nijmegen Institute for Cognition and Information, Radboud University Nijmegen, Nijmegen, The Netherlands.
J Neurophysiol. 2008 May;99(5):2264-80. doi: 10.1152/jn.00704.2007. Epub 2008 Mar 12.
To assess the effects of degrading canal cues for dynamic spatial orientation in human observers, we tested how judgments about visual-line orientation in space (subjective visual vertical task, SVV) and estimates of instantaneous body tilt (subjective body-tilt task, SBT) develop in the course of three cycles of constant-velocity roll rotation. These abilities were tested across the entire tilt range in separate experiments. For comparison, we also obtained SVV data during static roll tilt. We found that as tilt increased, dynamic SVV responses became strongly biased toward the head pole of the body axis (A-effect), as if body tilt was underestimated. However, on entering the range of near-inverse tilts, SVV responses adopted a bimodal pattern, alternating between A-effects (biased toward head-pole) and E-effects (biased toward feet-pole). Apart from an onset effect, this tilt-dependent pattern of systematic SVV errors repeated itself in subsequent rotation cycles with little sign of worsening performance. Static SVV responses were qualitatively similar and consistent with previous reports but showed smaller A-effects. By contrast, dynamic SBT errors were small and unimodal, indicating that errors in visual-verticality estimates were not caused by errors in body-tilt estimation. We discuss these results in terms of predictions from a canal-otolith interaction model extended with a leaky integrator and an egocentric bias mechanism. We conclude that the egocentric-bias mechanism becomes more manifest during constant velocity roll-rotation and that perceptual errors due to incorrect disambiguation of the otolith signal are small despite the decay of canal signals.
为了评估在人类观察者中降解通道线索对动态空间定向的影响,我们测试了在三个等速侧滚旋转周期过程中,空间中视觉线方向的判断(主观视觉垂直任务,SVV)和瞬时身体倾斜估计(主观身体倾斜任务,SBT)是如何发展的。在单独的实验中,在整个倾斜范围内对这些能力进行了测试。为了进行比较,我们还在静态侧滚倾斜期间获得了SVV数据。我们发现,随着倾斜度增加,动态SVV反应强烈偏向身体轴的头部极点(A效应),就好像身体倾斜被低估了一样。然而,当进入近乎反向倾斜范围时,SVV反应呈现双峰模式,在A效应(偏向头部极点)和E效应(偏向脚部极点)之间交替。除了起始效应外,这种与倾斜度相关的系统性SVV误差模式在随后的旋转周期中重复出现,几乎没有表现出性能恶化的迹象。静态SVV反应在性质上相似且与先前的报告一致,但显示出较小的A效应。相比之下,动态SBT误差较小且为单峰,表明视觉垂直度估计中的误差不是由身体倾斜估计中的误差引起的。我们根据一个扩展了泄漏积分器和自我中心偏差机制的半规管 - 耳石相互作用模型的预测来讨论这些结果。我们得出结论,自我中心偏差机制在等速侧滚旋转期间变得更加明显,并且尽管半规管信号衰减,但由于耳石信号的错误解歧导致的感知误差很小。