Department of Electrical and Electronic Engineering, Sami Shamoon College of Engineering, Ashdod, Israel.
Invest Ophthalmol Vis Sci. 2013 Jan 28;54(1):731-8. doi: 10.1167/iovs.12-10689.
The purpose of the current research is to understand if the different eye movement abnormalities in patients with the same neurologic disease are related to varied disease processes or, alternately, do different patients adopt different strategies to overcome a singular brain deficiency.
Using a magnetic search coil, we measured saccade dynamics, that is position and velocity waveforms, for patients diagnosed with spinocerebellar ataxia type 3 (SCA-3), also known as Machado-Joseph disease (MJD).
We observed that the saccadic waveform of the majority of the SCA-3 patients (7 of 10) exhibited dynamic overshoot, with the eye passing the desired endpoint and making a rapid correction before coming to rest. Patients with normal waveforms, that is with no dynamic overshoot, had saccades with relatively low peak velocity.
Velocity feedback in a closed loop control system is essential for providing a fast response without overshoot. Lack of a velocity feedback or an imbalance between position and velocity gains yields a tradeoff between response time and overshoot. While the goal of a saccade is to get to the desired position, models based on animal research suggest that the saccadic control also incorporates a velocity feedback. Results presented here indicated that all SCA-3 patients had deviations in the saccadic waveform, albeit of two types, either slow saccades or dynamic overshooting saccades. Using saccadic models based on animal research can explain how a single deficit, that is a mismatched velocity control of the motor error due to the disease, can yield these two different abnormalities in human patients.
本研究旨在探讨同一神经疾病患者的不同眼球运动异常是与不同的疾病过程相关，还是不同的患者采用不同的策略来克服单一的大脑缺陷。
我们使用磁搜索线圈测量了被诊断为脊髓小脑性共济失调 3 型（SCA-3），也称为 Machado-Joseph 病（MJD）的患者的眼球运动动力学，即位置和速度波形。
我们观察到大多数 SCA-3 患者（10 例中的 7 例）的眼跳波形表现出动态过冲，眼睛超过目标终点并在静止前快速校正。具有正常波形（即没有动态过冲）的患者的眼跳具有相对较低的峰值速度。
在闭环控制系统中，速度反馈对于提供无过冲的快速响应至关重要。缺乏速度反馈或位置和速度增益之间的不平衡会导致响应时间和过冲之间的权衡。虽然眼跳的目标是到达期望的位置，但基于动物研究的模型表明，眼跳控制还包含速度反馈。这里呈现的结果表明，所有 SCA-3 患者的眼跳波形都存在偏差，尽管有两种类型，要么是缓慢的眼跳，要么是动态的过冲眼跳。使用基于动物研究的眼跳模型可以解释单一缺陷，即由于疾病导致的运动误差的速度控制不匹配，如何导致人类患者出现这两种不同的异常。
