Congenital nystagmus: Hypotheses for its genesis and complex waveforms within a behavioral ocular motor system model
Congenital nystagmus: Hypotheses for its genesis and complex waveforms within a behavioral ocular motor system model
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DOI：
10.1167/4.7.7
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发表时间：
2004-01-01
影响因子：
1.8
通讯作者：
Dell'Osso, LF
中科院分区：
文献类型：
--
作者：
Jacobs, JB;Dell'Osso, LF
在能够表现出已知眼运动行为的眼运动系统（OMS）模型内模拟功能障碍的尝试已经提供了对正常视觉功能所需的OMS结构的有价值的洞察。先天性眼球震颤（CN）的摆动波形似乎是相当复杂的，由持续的正弦振荡中断制动扫视和中心凹扫视，其次是延长中心凹的时期。之前，我们验证了这些快速阶段是由与自愿扫视相同的机制产生的。我们提出了一个计算机模型的眼电机系统，模拟个人的反应与摆动CN（包括其可变波形）的基础上表现出的不稳定性的正常追求子系统和其与其他组件的正常眼电机控制系统的相互作用。使用红外线和磁搜索线圈眼电图的CN受试者的固定数据被用作我们模拟的模板。我们的OMS模型模拟了CN个体在固定过程中和对复杂刺激的反应中的数据。使用位置和速度传出复制来抑制失视是允许正常眼运动行为的关键因素。该模型对目标步、脉冲步、斜坡和步斜坡的响应支持对导致持续摆动的条件的假设性解释，以及将该潜在振荡塑造成众所周知的摆动CN波形家族的校正扫视响应的规则：摆动性（P）、假中央凹性（PP）、摆动性中央凹性扫视（P-fs）和假中央凹性扫视（PPfs）。位置误差决定了中心凹眼跳的幅度，而刻板制动眼跳不依赖于视觉信息。此外，我们提出了一种结构和操作方法的固定子系统，并使用它来延长低速度间隔后立即注视扫视。该模型的鲁棒性支持这一假设，即CN中看到的摆动性眼球震颤是由于正常追踪系统速度振荡的阻尼损失（功能上，它是追踪系统眼球震颤-PSN）。
Attempts to simulate dysfunction within ocular motor system (OMS) models capable of exhibiting known ocular motor behavior have provided valuable insight into the structure of the OMS required for normal visual function. The pendular waveforms of congenital nystagmus (CN) appear to be quite complex, composed of a sustained sinusoidal oscillation punctuated by braking saccades and foveating saccades followed by periods of extended foveation. Previously, we verified that these quick phases are generated by the same mechanism as voluntary saccades. We propose a computer model of the ocular motor system that simulates the responses of individuals with pendular CN (including its variable waveforms) based on the instability exhibited by the normal pursuit subsystem and its interaction with other components of the normal ocular motor control system. Fixation data from subjects with CN using both infrared and magnetic search coil oculography were used as templates for our simulations. Our OMS model simulates data from individuals with CN during fixation and in response to complex stimuli. The use of position and velocity efference copy to suppress oscillopsia is the key element in allowing for normal ocular motor behavior. The model's responses to target steps, pulse-steps, ramps, and step-ramps support the hypothetical explanation for the conditions that result in sustained pendular oscillation and the rules for the corrective saccadic responses that shape this underlying oscillation into the well-known family of pendular CN waveforms: pendular (P), pseudopendular (PP), pendular with foveating saccades (P-fs), and pseudopendular with foveating saccades (PPfs). Position error determined the saccadic amplitudes of foveating saccades, whereas stereotypical braking saccades were not dependent on visual information. Additionally, we propose a structure and method of operation for the fixation subsystem, and use it to prolong the low-velocity intervals immediately following foveating saccades. The model's robustness supports the hypothesis that the pendular nystagmus seen in CN is due to a loss of damping of the normal pursuit-system velocity oscillation (functionally, it is pursuit-system nystagmus-PSN).