Ho Cindy S, Giaschi Deborah E
Department of Ophthalmology and Visual Sciences, University of British Columbia, Children's and Women's Health Centre of British Columbia, Canada.
Vision Res. 2009 Dec;49(24):2891-901. doi: 10.1016/j.visres.2009.07.012. Epub 2009 Jul 27.
Maximum motion displacement (Dmax) is the largest dot displacement in a random-dot kinematogram (RDK) at which direction of motion can be correctly discriminated [Braddick, O. (1974). A short-range process in apparent motion. Vision Research, 14, 519-527]. For first-order RDKs, Dmax gets larger as dot size increases and/or dot density decreases. It has been suggested that this increase in Dmax reflects greater involvement of high-level feature-matching motion mechanisms and less dependence on low-level motion detectors [Sato, T. (1998). Dmax: Relations to low- and high-level motion processes. In T. Watanabe (Ed.), High-level motion processing, computational, neurobiological, and psychophysical perspectives (pp. 115-151). Boston: MIT Press]. Recent psychophysical findings [Ho, C. S., & Giaschi, D. E. (2006). Deficient maximum motion displacement in amblyopia. Vision Research, 46, 4595-4603; Ho, C. S., & Giaschi, D. E. (2007). Stereopsis-dependent deficits in maximum motion displacement. Vision Research, 47, 2778-2785] suggest that this "switch" from low-level to high-level motion processing is also observed in children with anisometropic and strabismic amblyopia as RDK dot size is increased and/or dot density is decreased. However, both high- and low-level Dmax were reduced relative to controls. In this study, we used functional MRI to determine the motion-sensitive areas that may account for the reduced Dmax in amblyopia In the control group, low-level RDKs elicited stronger responses in low-level (posterior occipital) areas and high-level RDKs elicited a greater response in high-level (extra-striate occipital-parietal) areas when activation for high-level RDKs was compared to that for low-level RDKs. Participants with anisometropic amblyopia showed the same pattern of cortical activation although extent of activation differences was less than in controls. For those with strabismic amblyopia, there was almost no difference in the cortical activity for low-level and high-level RDKs, and activation was reduced relative to the other groups. Differences in the extent of cortical activation may be related to amblyogenic subtype.
最大运动位移（Dmax）是随机点运动图（RDK）中能正确辨别运动方向的最大点位移[布拉迪克，O.（1974年）。表观运动中的一个短程过程。《视觉研究》，14，519 - 527]。对于一阶RDK，随着点大小增加和/或点密度降低，Dmax会变大。有人认为，Dmax的这种增加反映了高级特征匹配运动机制的更多参与以及对低级运动探测器的更少依赖[佐藤，T.（1998年）。Dmax：与低级和高级运动过程的关系。载于T.渡边（编），《高级运动处理，计算、神经生物学和心理物理学视角》（第115 - 151页）。波士顿：麻省理工学院出版社]。最近的心理物理学研究结果[何，C.S.，&贾斯基，D.E.（2006年）。弱视中最大运动位移不足。《视觉研究》，46，4595 - 4603；何，C.S.，&贾斯基，D.E.（2007年）。最大运动位移中依赖立体视觉的缺陷。《视觉研究》，47，2778 - 2785]表明，随着RDK点大小增加和/或点密度降低，在屈光参差性和斜视性弱视儿童中也观察到了这种从低级到高级运动处理的“转换”。然而，相对于对照组，高级和低级Dmax均降低。在本研究中，我们使用功能磁共振成像来确定可能导致弱视中Dmax降低的运动敏感区域。在对照组中，当将高级RDK的激活与低级RDK的激活进行比较时，低级RDK在低级（枕叶后部）区域引发更强的反应，而高级RDK在高级（枕叶 - 顶叶纹外）区域引发更大的反应。屈光参差性弱视参与者表现出相同的皮层激活模式，尽管激活差异的程度小于对照组。对于斜视性弱视患者，低级和高级RDK的皮层活动几乎没有差异，并且相对于其他组激活降低。皮层激活程度的差异可能与弱视亚型有关。
