Busettini Claudio, Christy Jennifer Braswell
Department of Physical Therapy, University of Alabama at Birmingham, Birmingham, Alabama *
Optom Vis Sci. 2018 Nov;95(11):986-1003. doi: 10.1097/OPX.0000000000001291.
Saccades present a direct relationship between the size of the movement (SACSIZE) and its peak velocity (SACPEAK), the main sequence, which is traditionally quantified using the model SACPEAK = Vmax × (1 - e). This study shows that Vmax and SAT are not veridical indicators of saccadic dynamics.
Alterations in saccadic dynamics are used as a diagnostic tool. Are the 95% reference ranges (RRs) of Vmax and SAT correctly quantifying the variability in saccadic dynamics of a population?
Visually driven horizontal and vertical saccades were acquired from 116 normal subjects using the Neuro Kinetics Inc. Concussion Protocol with a 100-Hz I-Portal NOTC Vestibular System, and the main sequence models were computed.
The 95% RRs of Vmax, the asymptotic peak velocity, and SAT, the speed of the exponential rise toward Vmax, were quite large. The finding of a strong correlation between Vmax and SAT suggests that their variability might be, in part, a computational interaction. In fact, the interplay between the two parameters greatly reduced the actual peak velocity variability for saccades less than 15°. This correlation was not strong enough to support the adoption of a one-parameter model, where Vmax is estimated from SAT using the regression parameters. We also evaluated the effects of interpolating the position data to a simulated acquisition rate of 1 kHz. Interpolation had no effect on the population average of Vmax and brought a decrease of the average SAT by roughly 8%.
The 95% RRs of Vmax and SAT, treated as independent entities, are not a veridical representation of the variability in saccadic dynamics inside a population, especially for small saccades. We introduce a novel three-step method to determine if a data set is inside or outside a reference population that takes into account the correlation between Vmax and SAT.
扫视运动呈现出运动幅度(SACSIZE)与其峰值速度(SACPEAK)之间的直接关系,即主序列,传统上使用模型SACPEAK = Vmax × (1 - e)进行量化。本研究表明,Vmax和SAT并非扫视动力学的真实指标。
扫视动力学的改变被用作一种诊断工具。Vmax和SAT的95%参考范围(RRs)是否正确量化了人群扫视动力学的变异性?
使用Neuro Kinetics Inc.脑震荡协议和100赫兹I-Portal NOTC前庭系统,从116名正常受试者中获取视觉驱动的水平和垂直扫视运动,并计算主序列模型。
Vmax(渐近峰值速度)和SAT(向Vmax指数上升的速度)的95%RRs相当大。Vmax和SAT之间存在强相关性,这表明它们的变异性可能部分是一种计算相互作用。事实上,对于小于15°的扫视运动,这两个参数之间的相互作用大大降低了实际峰值速度的变异性。这种相关性不够强,不足以支持采用单参数模型,即使用回归参数从SAT估计Vmax。我们还评估了将位置数据内插到模拟采集率1kHz的影响。内插对Vmax的总体平均值没有影响,而使平均SAT降低了约8%。
将Vmax和SAT的95%RRs视为独立实体时,它们并非人群中扫视动力学变异性的真实表征,尤其是对于小幅度扫视运动。我们引入了一种新颖的三步法,以确定数据集是在参考人群之内还是之外,该方法考虑了Vmax和SAT之间的相关性。