Demer Joseph L, Clark Robert A
Department of Ophthalmology, David Geffen Medical School, University of California, Los Angeles, California; and Department of Neurology, David Geffen Medical School, University of California, Los Angeles, California
Department of Ophthalmology, David Geffen Medical School, University of California, Los Angeles, California; and.
J Neurophysiol. 2014 Aug 15;112(4):845-55. doi: 10.1152/jn.00649.2013. Epub 2014 May 21.
Activity in horizontal rectus extraocular muscles (EOMs) was investigated by magnetic resonance imaging (MRI) of humans during asymmetric convergence to a monocularly aligned target at 15-cm distance or monocular fixation of afocal targets placed over a wide range of conjugate abduction through adduction. Cross sections and posterior partial volumes (PPVs) of EOMs were determined from quasi-coronal image planes and were separately analyzed in the inferior vs. superior compartments, defined by lines bisecting their maximum vertical dimensions. Both inferior and superior compartments of medial (MR) and lateral (LR) rectus exhibited contractile changes in PPV and maximum cross section for both asymmetric convergence and a comparable range of conjugate adduction. Both LR compartments, and the inferior MR compartment, exhibited similar decreases in contractility correlating with relaxation during both convergence and conjugate adduction. In contrast, the superior MR compartment exhibited roughly three times the contractility in conjugate adduction as in similar-magnitude convergence. In the aligned eye that did not move during convergence, summed contractility in all compartments of MR and LR exhibited corelaxation consistent with published EOM force measurements in this paradigm (Miller JM, Bockisch CJ, Pavlovski DS. J Neurophysiol 87: 2421-2433, 2002; Miller JM, Davison RC, Gamlin PD. J Neurophysiol 105: 2863-2873, 2011). The superior MR compartment also exhibited significantly greater contractility than the other compartments over the maximum achievable horizontal globe rotation from abduction to adduction. These findings suggest that the superior MR compartment is controlled differentially from the inferior compartment and suggest that its activity is reduced during convergence as a component of generally altered extraocular mechanics.
通过磁共振成像（MRI）对人类水平直肌眼外肌（EOMs）进行了研究，研究内容为在向15厘米距离处单眼对齐目标进行不对称集合时，或在通过内收进行大范围共轭外展时对无焦目标进行单眼注视的情况。从准冠状图像平面确定EOMs的横截面和后部分体积（PPV），并分别在由平分其最大垂直尺寸的线定义的下部分隔和上部分隔中进行分析。内直肌（MR）和外直肌（LR）的下部分隔和上部分隔在不对称集合和相当范围的共轭内收时，PPV和最大横截面均表现出收缩变化。两个LR分隔以及MR下部分隔在集合和共轭内收时均表现出与松弛相关的收缩性类似下降。相比之下，MR上部分隔在共轭内收时的收缩性大约是类似幅度集合时的三倍。在集合过程中不移动的对齐眼中，MR和LR所有分隔的总收缩性表现出协同松弛，这与该范式中已发表的EOM力测量结果一致（Miller JM、Bockisch CJ、Pavlovski DS。《神经生理学杂志》87：2421 - 2433，2002；Miller JM、Davison RC、Gamlin PD。《神经生理学杂志》105：2863 - 2873，2011）。在从外展到内收的最大可实现水平眼球旋转范围内，MR上部分隔的收缩性也明显大于其他分隔。这些发现表明，MR上部分隔与下部分隔的控制方式不同，并且表明其活动在集合过程中作为眼外力学普遍改变的一个组成部分而降低。
