Yasuda K, Fushiki H, Maruyama M, Watanabe Y
Department of Otolaryngology, Toyama Medical and Pharmaceutical University, 2630 Sugitani, Toyama Toyama 930-0194, Japan.
Brain Res. 2003 Nov 21;991(1-2):65-70. doi: 10.1016/s0006-8993(03)03536-4.
When the head is tilted away from the upright position immediately after termination of earth-vertical axis (EVA) head rotation at a constant velocity, the rotation axis of postrotatory nystagmus (PRN) is gradually directed toward gravity (spatial reorientation). During roll tilt, the extent of the axis shift varies among species. In cats, the reorientation is limited to about 30-45 degrees of head tilt. In the present study, we examined features of PRN during pitch tilt in cats. The animals were rotated about EVA at a constant velocity of 100 degrees /s for 120 s. Within 2 s after stopping EVA rotation, the animals were tilted toward the pitch plane by as much as +/-90 degrees (nose-down or nose-up) in steps of 15 degrees. Eye movements were measured with 3D magnetic search coils. The angle of the PRN plane and its slow phase eye velocity (SPV) were measured. The duration of PRN decreased as pitch tilt increased regardless of whether the direction was nose-up or nose-down. The mean time constant of SPV was significantly longer for nose-up than for nose-down. PRN maintained its horizontal orientation without any vertical drift during pitch tilt, but there was little reorientation toward gravity. That is, no significant torsional component of SPV emerged to reorient the eyes according to gravity. Our results indicate that spatial reorientation depends on head orientation. For the PRN responses after pitch tilts in cats, the interactions of semicircular canal and otolith inputs in the central vestibular system might be vestigial.
当以恒定速度终止地垂直轴（EVA）头部旋转后，头部立即从直立位置倾斜时，旋转后眼震（PRN）的旋转轴会逐渐指向重力方向（空间重新定向）。在侧倾倾斜过程中，轴偏移的程度在不同物种间有所不同。在猫中，重新定向仅限于头部倾斜约30 - 45度。在本研究中，我们研究了猫在俯仰倾斜过程中PRN的特征。动物以100度/秒的恒定速度绕EVA旋转120秒。在停止EVA旋转后的2秒内，动物以15度的步长向俯仰平面倾斜多达+/-90度（鼻朝下或鼻朝上）。用三维磁性搜索线圈测量眼动。测量PRN平面的角度及其慢相眼速度（SPV）。无论方向是鼻朝上还是鼻朝下，PRN的持续时间都随着俯仰倾斜的增加而减少。鼻朝上时SPV的平均时间常数明显长于鼻朝下时。在俯仰倾斜过程中，PRN保持其水平方向，没有任何垂直漂移，但几乎没有向重力方向的重新定向。也就是说，没有明显的SPV扭转分量出现以根据重力重新定向眼睛。我们的结果表明，空间重新定向取决于头部方向。对于猫在俯仰倾斜后的PRN反应，中央前庭系统中半规管和耳石输入的相互作用可能是退化的。
