Maruyama Masaki, Fenwick Peter Bc, Ioannides Andreas A
Laboratory for Human Brain Dynamics, RIKEN Brain Science Institute, 2-1 Hirosawa, Wakoshi, Saitama 351-0198, Japan .
Nonlinear Biomed Phys. 2010 Jun 3;4 Suppl 1(Suppl 1):S10. doi: 10.1186/1753-4631-4-S1-S10.
Saccadic eye movements align the two eyes precisely to foveate a target. Trial-by-trial variance of eye movement is always observed within an identical experimental condition. This has often been treated as experimental error without addressing its significance. The present study examined statistical linkages between the two eyes' movements, namely interocular yoking, for the variance of eye position and velocity.
Horizontal saccadic movements were recorded from twelve right-eye-dominant subjects while they decided on saccade direction in Go-Only sessions and on both saccade execution and direction in Go/NoGo sessions. We used infrared corneal reflection to record simultaneously and independently the movement of each eye. Quantitative measures of yoking were provided by mutual information analysis of eye position or velocity, which is sensitive to both linear and non-linear relationships between the eyes' movements. Our mutual information analysis relied on the variance of the eyes movements in each experimental condition. The range of movements for each eye varies for different conditions so yoking was further studied by comparing GO-Only vs. Go/NoGo sessions, leftward vs. rightward saccades.
Mutual information analysis showed that velocity yoking preceded positional yoking. Cognitive load increased trial variances of velocity with no increase in velocity yoking, suggesting that cognitive load may alter neural processes in areas to which oculomotor control is not tightly linked. The comparison between experimental conditions showed that interocular linkage in velocity variance of the right eye lagged that of the left eye during saccades.
We conclude quantitative measure of interocular yoking based on trial-to-trial variance within a condition, as well as variance between conditions, provides a powerful tool for studying the binocular movement mechanism.
扫视眼动可精确对齐双眼以注视目标。在相同实验条件下，眼动的逐次试验方差总是存在的。这常常被视为实验误差而未探讨其意义。本研究考察了双眼运动之间的统计关联，即双眼共轭，涉及眼位和速度的方差。
记录了12名右眼优势受试者的水平扫视运动，这些受试者在仅执行任务的实验环节中决定扫视方向，在执行/不执行任务的实验环节中决定扫视执行和方向。我们使用红外角膜反射同时独立记录每只眼睛的运动。通过对眼位或速度进行互信息分析来提供共轭的定量测量，互信息分析对双眼运动之间的线性和非线性关系均敏感。我们的互信息分析依赖于每个实验条件下眼动的方差。不同条件下每只眼睛的运动范围不同，因此通过比较仅执行任务与执行/不执行任务的实验环节、向左与向右扫视，进一步研究共轭。
互信息分析表明速度共轭先于位置共轭。认知负荷增加了速度的逐次试验方差，但速度共轭未增加，这表明认知负荷可能改变了与眼球运动控制联系不紧密区域的神经过程。实验条件之间的比较表明，扫视过程中右眼速度方差的眼间关联滞后于左眼。
我们得出结论，基于条件内逐次试验方差以及条件间方差的双眼共轭定量测量，为研究双眼运动机制提供了一个有力工具。
