Cox Philip G, Jeffery Nathan
Division of Human Anatomy and Cell Biology, School of Biomedical Sciences, University of Liverpool, Liverpool, UK.
J Anat. 2008 Nov;213(5):583-96. doi: 10.1111/j.1469-7580.2008.00983.x.
The vestibulo-ocular reflex (VOR) exacts compensatory movements of the extraocular muscles in response to stimulation of the semicircular canals to allow gaze fixation during head movements. In this study, the spatial relationships of these muscles and canals were investigated to assess their relative alignments in mammalian species commonly used in studies of the VOR. The head region of each specimen was scanned using magnetic resonance imaging and 28 anatomical landmarks were recorded from the images to define the six extraocular muscles and the anatomical planes of the three semicircular canals. The vector rotation of a semicircular canal that does not stimulate either of its two sister canals, referred to as the prime direction, was also calculated as an estimate of the maximal response plane. Significant misalignments were found between the extraocular muscles and the canals by which they are principally stimulated in most of the species under study. The deviations from parallel orientation were most pronounced in the human and rabbit samples. There were also significant departures from orthogonality between the semicircular canals in most species. Only the guinea pig displayed no significant difference from 90 degrees in any of its three inter-canal angles, although humans and rabbits deviated from orthogonality in just one semicircular canal pair - the anterior and posterior canals. The prime directions were found to deviate considerably from the anatomical canal planes (by over 20 degrees in rats). However, these deviations were not always compensatory, i.e. prime planes were not always more closely aligned with the muscle planes. Results support the view that the vestibular frame remains relatively stable and that the spatial mismatch with the extraocular co-ordinate frame is principally driven by realignment of the muscles as a result of changes in the position of the orbits within the skull (orbital convergence and frontation).
前庭眼反射（VOR）可引发眼外肌的代偿性运动，以响应半规管的刺激，从而在头部运动时保持注视稳定。在本研究中，对这些肌肉和半规管的空间关系进行了研究，以评估它们在常用于VOR研究的哺乳动物物种中的相对排列情况。使用磁共振成像对每个标本的头部区域进行扫描，并从图像中记录28个解剖学标志点，以确定六条眼外肌和三个半规管的解剖平面。还计算了一条不刺激其两个姐妹半规管中任何一个的半规管的矢量旋转，即主方向，作为最大反应平面的估计值。在所研究的大多数物种中，发现眼外肌与其主要受刺激的半规管之间存在明显的错位。在人类和兔子样本中，与平行方向的偏差最为明显。大多数物种的半规管之间也明显偏离正交性。只有豚鼠的三个半规管间角度中的任何一个与90度均无显著差异，尽管人类和兔子仅在一对半规管——前半规管和后半规管中偏离正交性。发现主方向与解剖学半规管平面有相当大的偏差（大鼠中超过20度）。然而，这些偏差并不总是具有代偿性，即主平面并不总是与肌肉平面更紧密地对齐。结果支持这样一种观点，即前庭框架相对稳定，与眼外坐标框架的空间不匹配主要是由于颅骨内眼眶位置变化（眼眶会聚和前位化）导致肌肉重新排列所致。
