Boon Mei Ying, Henry Bruce I, Suttle Catherine M, Dain Stephen J
School of Optometry and Vision Science, UNSW, Sydney, NSW, Australia.
J Vis. 2008 Jan 14;8(1):6.1-21. doi: 10.1167/8.1.6.
Visual evoked potentials (VEPs) may be analyzed by examination of the morphology of their components, such as negative (N) and positive (P) peaks. However, methods that rely on component identification may be unreliable when dealing with responses of complex and variable morphology; therefore, objective methods are also useful. One potentially useful measure of the VEP is the correlation dimension. Its relevance to the visual system was investigated by examining its behavior when applied to the transient VEP in response to a range of chromatic contrasts (42%, two times psychophysical threshold, at psychophysical threshold) and to the visually unevoked response (zero contrast). Tests of nonlinearity (e.g., surrogate testing) were conducted. The correlation dimension was found to be negatively correlated with a stimulus property (chromatic contrast) and a known linear measure (the Fourier-derived VEP amplitude). It was also found to be related to visibility and perception of the stimulus such that the dimension reached a maximum for most of the participants at psychophysical threshold. The latter suggests that the correlation dimension may be useful as a diagnostic parameter to estimate psychophysical threshold and may find application in the objective screening and monitoring of congenital and acquired color vision deficiencies, with or without associated disease processes.
视觉诱发电位（VEPs）可通过检查其成分的形态，如负（N）峰和正（P）峰来进行分析。然而，在处理形态复杂多变的反应时，依赖成分识别的方法可能不可靠；因此，客观方法也很有用。VEP的一种潜在有用的测量方法是关联维数。通过检查其应用于瞬态VEP时的行为，研究了其与视觉系统的相关性，该瞬态VEP是对一系列色度对比度（42%，心理物理学阈值的两倍，处于心理物理学阈值）以及视觉未诱发反应（零对比度）的响应。进行了非线性测试（例如，替代测试）。发现关联维数与刺激属性（色度对比度）和一种已知的线性测量（傅里叶导出的VEP振幅）呈负相关。还发现它与刺激的可见性和感知有关，以至于对于大多数参与者来说，关联维数在心理物理学阈值时达到最大值。后者表明关联维数可能作为估计心理物理学阈值的诊断参数有用，并可能在先天性和后天性色觉缺陷的客观筛查和监测中找到应用，无论是否伴有相关疾病过程。
