Sinn Petra, Engbert Ralf
Universität Potsdam, Am Neuen Palais 10, 14469 Potsdam, Germany.
Vision Res. 2016 Jan;118:132-43. doi: 10.1016/j.visres.2015.05.012. Epub 2015 Jun 4.
Natural vision is characterized by alternating sequences of rapid gaze shifts (saccades) and fixations. During fixations, microsaccades and slower drift movements occur spontaneously, so that the eye is never motionless. Theoretical models of fixational eye movements predict that microsaccades are dynamically coupled to slower drift movements generated immediately before microsaccades, which might be used as a criterion to distinguish microsaccades from small voluntary saccades. Here we investigate a sequential scanning task, where participants generate goal-directed saccades and microsaccades with overlapping amplitude distributions. We show that properties of microsaccades are correlated with precursory drift motion, while amplitudes of goal-directed saccades do not dependent on previous drift epochs. We develop and test a mathematical model that integrates goal-directed and fixational eye movements, including microsaccades. Using model simulations, we reproduce the experimental finding of correlations within fixational eye movement components (i.e., between physiological drift and microsaccades) but not between goal-directed saccades and fixational drift motion. These results lend support to a functional difference between microsaccades and goal-directed saccades, while, at the same time, both types of behavior may be part of an oculomotor continuum that is quantitatively described by our mathematical model.
自然视觉的特点是快速的注视转移（扫视）和注视交替出现。在注视过程中，微扫视和较慢的漂移运动自发发生，因此眼睛永远不会静止不动。注视性眼动的理论模型预测，微扫视与微扫视之前立即产生的较慢漂移运动动态耦合，这可能被用作区分微扫视和小的随意扫视的标准。在这里，我们研究了一种顺序扫描任务，参与者在该任务中产生具有重叠幅度分布的目标导向扫视和微扫视。我们表明，微扫视的特性与前驱漂移运动相关，而目标导向扫视的幅度不依赖于先前的漂移阶段。我们开发并测试了一个整合目标导向和注视性眼动（包括微扫视）的数学模型。通过模型模拟，我们重现了注视性眼动成分之间（即生理漂移和微扫视之间）相关性的实验结果，但目标导向扫视与注视性漂移运动之间没有相关性。这些结果支持了微扫视和目标导向扫视之间的功能差异，同时，这两种行为可能都是我们的数学模型定量描述的眼动连续体的一部分。
