Telford L, Seidman S H, Paige G D
Department of Neurology and the Center for Visual Science, University of Rochester, NY 14642, USA.
Exp Brain Res. 1998 Jan;118(1):115-25. doi: 10.1007/s002210050261.
Natural head movements include angular and linear components of motion. Two classes of vestibulo-ocular reflex (VOR), mediated by the semicircular canals and otoliths (the angular and linear VOR, or AVOR and LVOR, respectively), compensate for head movements and help maintain binocular fixation on targets in space. In this study, AVOR/LVOR interactions were quantified during complex head motion over a broad range of fixation distances at a fixed stimulus frequency of 4.0 Hz. Binocular eye movements were recorded (search-coil technique) in squirrel monkeys while fixation distance (assessed by vergence) was varied using brief presentations of earth-fixed targets at various distances. Stimuli consisted of rotations around an earth-vertical axis and therefore always activated the AVOR. Horizontal and vertical AVORs were assessed when the head was centered over the axis of rotation and oriented upright (UP) and right-side-down (RD), respectively. AVOR gains increased slightly with increasing vergence in darkness, as expected given the small anterior position of the eyes in the head. Combined AVOR/LVOR responses were recorded when subjects were displaced eccentrically from the rotation axis. Eccentric rotations activated the AVOR just as when the head was centered, but added a translational stimulus which generated an LVOR component in response to interaural (IA) or dorsoventral (DV) tangential accelerations, depending on whether the head was UP or RD, respectively. When the head was eccentric and facing nose-out, the AVOR and LVOR produced ocular responses in the same plane and direction (coplanar and synergistic), and response magnitudes increased with increasing vergence. With the head facing nose-in, AVOR and LVOR response components were oppositely directed (coplanar and antagonistic). The AVOR dominated the response when fixation distance was far, and phase was compensatory for head rotation. As fixation distance decreased toward the rotation axis, responses declined to near zero, and when fixation distance approached even closer, the LVOR component dominated and response phase inverted. The same pattern was observed for both horizontal (head UP) and vertical (head RD) responses. The LVOR was recorded directly by rotating subjects eccentrically but in the nose-up (NU) orientation. The AVOR then generated torsional responses to head roll, coexistent with either horizontal or vertical LVOR responses to tangential acceleration when the subject was oriented head-out or right-side-out, respectively. Only the LVOR response components were modulated by vergence. A vectorial analysis of AVOR, LVOR, and combined responses supports the conclusion that AVOR and LVOR response components combine linearly during complex head motion.
自然头部运动包括角向和线性运动成分。两类前庭眼反射（VOR），分别由半规管和耳石介导（即角向VOR和线性VOR，或分别为AVOR和LVOR），可补偿头部运动并有助于保持双眼对空间中目标的注视。在本研究中，在固定刺激频率4.0Hz下，对广泛注视距离范围内的复杂头部运动期间的AVOR/LVOR相互作用进行了量化。在松鼠猴中记录双眼眼动（搜索线圈技术），同时通过短暂呈现不同距离的固定于地面的目标来改变注视距离（通过辐辏评估）。刺激包括绕地球垂直轴的旋转，因此总是激活AVOR。当头部位于旋转轴上方且分别直立（UP）和右侧向下（RD）时，评估水平和垂直AVOR。正如预期的那样，由于眼睛在头部的前方位置较小，在黑暗中，AVOR增益随辐辏增加而略有增加。当受试者偏离旋转轴偏心位移时，记录AVOR/LVOR联合反应。偏心旋转激活AVOR的方式与头部居中时相同，但增加了一个平移刺激，该刺激会根据头部是UP还是RD分别产生一个响应耳间（IA）或背腹（DV）切向加速度的LVOR成分。当头部偏心且鼻尖向外时，AVOR和LVOR在同一平面和方向上产生眼动反应（共面且协同），且反应幅度随辐辏增加而增加。当头部鼻尖向内时，AVOR和LVOR反应成分方向相反（共面且拮抗）。当注视距离远时，AVOR主导反应，且相位对头部旋转具有补偿性。随着注视距离向旋转轴减小，反应下降至接近零，当注视距离更接近时，LVOR成分主导且反应相位反转。水平（头部UP）和垂直（头部RD）反应均观察到相同模式。通过使受试者偏心旋转但鼻尖向上（NU）取向直接记录LVOR。当受试者分别鼻尖向外或右侧向外时，AVOR随后会对头部侧倾产生扭转反应，与对切向加速度的水平或垂直LVOR反应共存。只有LVOR反应成分受辐辏调节。对AVOR、LVOR和联合反应的矢量分析支持以下结论：在复杂头部运动期间，AVOR和LVOR反应成分线性组合。
