Pomante A, Selen L P J, Medendorp W P
Radboud University, Donders Institute for Brain, Cognition and Behaviour, Nijmegen, The Netherlands
Radboud University, Donders Institute for Brain, Cognition and Behaviour, Nijmegen, The Netherlands.
J Neurophysiol. 2017 Oct 1;118(4):2499-2506. doi: 10.1152/jn.00439.2017. Epub 2017 Aug 16.
The vestibular system provides information for spatial orientation. However, this information is ambiguous: because the otoliths sense the gravitoinertial force, they cannot distinguish gravitational and inertial components. As a consequence, prolonged linear acceleration of the head can be interpreted as tilt, referred to as the somatogravic effect. Previous modeling work suggests that the brain disambiguates the otolith signal according to the rules of Bayesian inference, combining noisy canal cues with the a priori assumption that prolonged linear accelerations are unlikely. Within this modeling framework the noise of the vestibular signals affects the dynamic characteristics of the tilt percept during linear whole-body motion. To test this prediction, we devised a novel paradigm to psychometrically characterize the dynamic visual vertical-as a proxy for the tilt percept-during passive sinusoidal linear motion along the interaural axis (0.33 Hz motion frequency, 1.75 m/s peak acceleration, 80 cm displacement). While subjects (=10) kept fixation on a central body-fixed light, a line was briefly flashed (5 ms) at different phases of the motion, the orientation of which had to be judged relative to gravity. Consistent with the model's prediction, subjects showed a phase-dependent modulation of the dynamic visual vertical, with a subject-specific phase shift with respect to the imposed acceleration signal. The magnitude of this modulation was smaller than predicted, suggesting a contribution of nonvestibular signals to the dynamic visual vertical. Despite their dampening effect, our findings may point to a link between the noise components in the vestibular system and the characteristics of dynamic visual vertical. A fundamental question in neuroscience is how the brain processes vestibular signals to infer the orientation of the body and objects in space. We show that, under sinusoidal linear motion, systematic error patterns appear in the disambiguation of linear acceleration and spatial orientation. We discuss the dynamics of these illusory percepts in terms of a dynamic Bayesian model that combines uncertainty in the vestibular signals with priors based on the natural statistics of head motion.
前庭系统为空间定向提供信息。然而，这些信息具有模糊性：由于耳石感知重力惯性力，它们无法区分重力和惯性分量。因此，头部的长时间线性加速度可被解释为倾斜，这被称为躯体重力效应。先前的建模工作表明，大脑根据贝叶斯推理规则消除耳石信号的模糊性，将有噪声的半规管线索与长时间线性加速度不太可能出现的先验假设相结合。在此建模框架内，前庭信号的噪声会影响线性全身运动期间倾斜感知的动态特性。为了验证这一预测，我们设计了一种新颖的范式，通过心理测量来表征在沿双耳轴的被动正弦线性运动（运动频率0.33Hz，峰值加速度1.75m/s，位移80cm）期间作为倾斜感知替代指标的动态视觉垂直线。当受试者（n = 10）注视中央身体固定的灯光时，在运动的不同阶段短暂闪烁一条线（5毫秒），其方向必须相对于重力进行判断。与模型预测一致，受试者表现出动态视觉垂直线的相位依赖性调制，相对于施加的加速度信号存在个体特异性的相位偏移。这种调制的幅度小于预测值，表明非前庭信号对动态视觉垂直线有贡献。尽管有抑制作用，我们的发现可能指向前庭系统中的噪声成分与动态视觉垂直线特征之间的联系。神经科学中的一个基本问题是大脑如何处理前庭信号以推断身体和空间中物体的方向。我们表明，在正弦线性运动下，线性加速度和空间定向的解模糊过程中会出现系统误差模式。我们根据动态贝叶斯模型讨论这些错觉感知的动态，该模型将前庭信号的不确定性与基于头部运动自然统计的先验相结合。
