Ko Hee-Kyoung, Snodderly D Max, Poletti Martina
Department of Neuroscience, Institute for Neuroscience, and Center for Perceptual Systems, University of Texas at Austin, United States.
Department of Psychological and Brain Sciences, Boston University, Boston, MA 02215, United States.
Vision Res. 2016 May;122:93-104. doi: 10.1016/j.visres.2016.03.006. Epub 2016 Apr 17.
Intersaccadic periods of fixation are characterized by incessant retinal motion due to small eye movements. While these movements are often disregarded as noise, the temporal modulations they introduce to retinal receptors are significant. However, analysis of these input modulations is challenging because the intersaccadic eye motion is close to the resolution limits of most eyetrackers, including widespread pupil-based video systems. Here, we analyzed in depth the limits of two high-precision eyetrackers, the Dual-Purkinje Image and the scleral search coil, and compared the intersaccadic eye movements of humans to those of a non-human primate. By means of a model eye we determined that the resolution of both techniques is sufficient to reliably measure intersaccadic ocular activity up to approximately 80Hz. Our results show that the characteristics of ocular drift are remarkably similar in the two species; a clear deviation from a scale-invariant spectrum occurs in the range between 50 and 100Hz, generally attributed to ocular tremor, leading to intersaccadic retinal speeds as high as 1.5deg/s. The amplitude of this deviation differs on the two axes of motion. In addition to our experimental observations, we suggest basic guidelines to evaluate the performance of eyetrackers and to optimize experimental conditions for the measurement of ocular drift and tremor.
扫视间的注视期具有因微小眼球运动导致的视网膜持续运动的特征。虽然这些运动常被视为噪声而被忽视，但它们给视网膜感受器带来的时间调制是显著的。然而，对这些输入调制的分析具有挑战性，因为扫视间的眼球运动接近大多数眼动仪（包括广泛使用的基于瞳孔的视频系统）的分辨率极限。在这里，我们深入分析了两种高精度眼动仪——双浦肯野图像眼动仪和巩膜搜索线圈眼动仪的局限性，并将人类的扫视间眼球运动与一种非人类灵长类动物的进行了比较。通过一个模型眼，我们确定这两种技术的分辨率足以可靠地测量高达约80Hz的扫视间眼动活性。我们的结果表明，这两个物种的眼漂移特征非常相似；在50到100Hz的范围内出现了明显偏离尺度不变谱的情况，这通常归因于眼震颤，导致扫视间视网膜速度高达1.5度/秒。这种偏差的幅度在两个运动轴上有所不同。除了我们的实验观察结果外，我们还提出了评估眼动仪性能以及优化测量眼漂移和眼震颤实验条件的基本指导原则。
