Data_Sheet_1_Stochastic Physiological Gaze-Evoked Nystagmus With Slow Centripetal Drift During Fixational Eye Movements at Small Gaze Eccentricities.PDF

Involuntary eye movement during gaze (GZ) fixation, referred to as fixational eye movement (FEM), consists of two types of components: a Brownian motion like component called drifts-tremor (DRT) and a ballistic component called microsaccade (MS) with a mean saccadic amplitude of about 0.3° and a mean inter-MS interval of about 0.5 s. During GZ fixation in healthy people in an eccentric position, typically with an eccentricity more than 30°, eyes exhibit oscillatory movements alternating between centripetal drift and centrifugal saccade with a mean saccadic amplitude of about 1° and a period in the range of 0.5–1.0 s, which has been known as the physiological gaze-evoked nystagmus (GEN). Here, we designed a simple experimental paradigm of GZ fixation on a target shifted horizontally from the front-facing position with fewer eccentricities. We found a clear tendency of centripetal DRT and centrifugal MS as in GEN, but with more stochasticity and with slower drift velocity compared to GEN, even during FEM at GZ positions with small eccentricities. Our results showed that the target shift-dependent balance between DRT and MS achieves the GZ bounded around each of the given targets. In other words, GZ relaxes slowly with the centripetal DRT toward the front-facing position during inter-MS intervals, as if there always exists a quasi-stable equilibrium posture in the front-facing position, and MS actions pull GZ intermittently back to the target position in the opposite direction to DRT.

凝视（GZ）固视过程中出现的非自主性眼动，即固视眼动（FEM），包含两类成分：一类是类似布朗运动的漂移震颤（DRT），另一类是弹道式的微扫视（MS），其平均扫视幅度约为0.3°，平均MS间期约为0.5秒。当健康个体处于偏心位置进行GZ固视时，通常偏心率超过30°，双眼会呈现出向心漂移与离心扫视交替的振荡运动，平均扫视幅度约为1°，周期处于0.5~1.0秒范围内，该现象被称为生理性凝视诱发性眼震（GEN）。本研究设计了一种简易的GZ固视实验范式，让被试固视从正面朝向位置水平移位、且偏心率更低的目标。我们观察到，与GEN类似，存在明确的向心DRT与离心MS趋势，但相较于GEN，即便在小偏心率GZ位置的FEM过程中，该现象也具有更强的随机性，且漂移速度更慢。研究结果表明，依赖目标移位的DRT与MS之间的平衡，使得GZ始终被约束在各给定目标附近。换言之，在MS间期内，GZ会通过向心DRT缓慢向正面朝向位置松弛，仿佛正面朝向位置始终存在准稳定平衡姿态；而MS动作则会间歇性地将GZ拉回与DRT方向相反的目标位置。