Department of Medicina Interna, Sezione di Fisiologia Umana, Universit`a di Perugia, Perugia, Italy.
J Physiol. 2013 Apr 1;591(7):1907-20. doi: 10.1113/jphysiol.2012.241182. Epub 2013 Jan 14.
Self-motion perception and the vestibulo-ocular reflex (VOR) were investigated in healthy subjects during asymmetric whole body yaw plane oscillations while standing on a platform in the dark. Platform oscillation consisted of two half-sinusoidal cycles of the same amplitude (40°) but different duration, featuring a fast (FHC) and a slow half-cycle (SHC). Rotation consisted of four or 20 consecutive cycles to probe adaptation further with the longer duration protocol. Self-motion perception was estimated by subjects tracking with a pointer the remembered position of an earth-fixed visual target. VOR was measured by electro-oculography. The asymmetric stimulation pattern consistently induced a progressive increase of asymmetry in motion perception, whereby the gain of the tracking response gradually increased during FHCs and decreased during SHCs. The effect was observed already during the first few cycles and further increased during 20 cycles, leading to a totally distorted location of the initial straight-ahead. In contrast, after some initial interindividual variability, the gain of the slow phase VOR became symmetric, decreasing for FHCs and increasing for SHCs. These oppositely directed adaptive effects in motion perception and VOR persisted for nearly an hour. Control conditions using prolonged but symmetrical stimuli produced no adaptive effects on either motion perception or VOR. These findings show that prolonged asymmetric activation of the vestibular system leads to opposite patterns of adaptation of self-motion perception and VOR. The results provide strong evidence that semicircular canal inputs are processed centrally by independent mechanisms for perception of body motion and eye movement control. These divergent adaptation mechanisms enhance awareness of movement toward the faster body rotation, while improving the eye stabilizing properties of the VOR.
在黑暗中站在平台上，研究人员对健康受试者进行了非对称全身体横摇平面摆动时的自身运动感知和前庭眼动反射（VOR）测试。平台摆动由两个相同幅度（40°）但不同持续时间的半正弦周期组成，分别为快（FHC）和慢半周期（SHC）。旋转由四个或 20 个连续周期组成，以更长的持续时间进一步探测适应。受试者通过用指针跟踪记住的固定在地球上的视觉目标的位置来估计自身运动感知。VOR 通过眼动描记术进行测量。不对称的刺激模式一致地引起运动感知的逐渐增加的不对称性，其中跟踪响应的增益在 FHC 期间逐渐增加，而在 SHC 期间逐渐减小。该效果在最初的几个周期中就已经观察到，并且在 20 个周期中进一步增加，导致初始直线的位置完全失真。相比之下，在最初的个体间变异性之后，慢相 VOR 的增益变得对称，FHC 时减小，SHC 时增加。这些在运动感知和 VOR 中的相反的适应性效应持续了将近一个小时。使用延长但对称的刺激的对照条件对运动感知或 VOR 都没有产生适应性影响。这些发现表明，前庭系统的长时间非对称激活会导致自身运动感知和 VOR 的适应模式相反。这些结果提供了有力的证据，表明半规管输入通过独立的机制在中枢被处理，用于感知身体运动和眼球运动控制。这些发散的适应机制增强了对更快身体旋转的运动的意识，同时提高了 VOR 的眼球稳定特性。
