Pfann K D, Keller E L, Miller J M
Smith-Kettlewell Eye Research Institute, San Francisco, CA 94115, USA.
Ann Biomed Eng. 1995 Jul-Aug;23(4):346-58. doi: 10.1007/BF02584436.
Several phenomenological models of the oculomotor mechanics that produce saccadic eye movements have been developed. These models have been based on measurements of macroscopic muscle and orbital tissue properties and measurements of eye kinematics during saccades. We recorded the forces generated by the medial and lateral recti during saccades in an alert, behaving monkey using chronically implanted force transducers. With this new data, we tested the ability of the classic saccade models to generate realistic muscle force profiles. Errors in the predictions of the classic saccade models led to a reexamination of the current models of extraocular muscle. Both a phenomenological, Hill-type muscle model and an approximation to Huxley's molecular level muscle model based on the cross-bridge mechanism of contraction (distribution moment model) were derived and studied for monkey extraocular muscle. Simulations of the distribution moment model led to insights suggesting (i) specific modifications in the lumped force/velocity relationship in the Hill-type model that resulted in this type of phenomenological model being able to generate realistic dynamics in extraocular muscle during saccades; (ii) the distribution of activity in the different fiber types in extraocular muscle may be central to the characteristics exhibited by the muscle during saccades; (iii) the transient properties of lengthening muscle such as yielding are not significant during saccades; and (iv) the series elastic component in active muscle may be predominantly generated by the elastic properties of the cross-bridges.
已经开发出了几种产生眼球快速运动的动眼力学现象学模型。这些模型基于对宏观肌肉和眼眶组织特性的测量以及扫视期间眼球运动学的测量。我们使用长期植入的力传感器记录了一只警觉的、行为正常的猴子在扫视过程中由内直肌和外直肌产生的力。利用这些新数据，我们测试了经典扫视模型生成逼真肌肉力曲线的能力。经典扫视模型预测中的误差导致了对当前眼外肌模型的重新审视。针对猴子眼外肌，推导并研究了一种现象学的希尔型肌肉模型以及基于收缩横桥机制的赫胥黎分子水平肌肉模型的近似模型（分布矩模型）。分布矩模型的模拟得出了一些见解，表明：（i）希尔型模型中集总力/速度关系的特定修改，使得这种现象学模型能够在扫视期间在眼外肌中产生逼真的动力学；（ii）眼外肌中不同纤维类型的活动分布可能是肌肉在扫视期间表现出的特征的核心；（iii）在扫视期间，拉长肌肉的瞬态特性（如屈服）并不显著；（iv）主动肌肉中的串联弹性成分可能主要由横桥的弹性特性产生。
