Rizzo M, Nawrot M
Department of Neurology, College of Medicine, University of Iowa, Iowa City, USA.
Brain. 1998 Dec;121 ( Pt 12):2259-70. doi: 10.1093/brain/121.12.2259.
Alzheimer's disease is the most prevalent cause of abnormal cognitive decline in older adults and commonly affects visual function. Recent evidence suggests that Alzheimer's disease impairs the processing of visual motion, but these conclusions are based on conflicting results in the few cases studied, and the processing of complex motion images has not been investigated. In the present study of motion processing in Alzheimer's disease we assessed visual functions in 63 adults: 41 with mild to moderate Alzheimer's disease (mean age 72.3 years) and 22 without dementia (mean age 71.7 years). Processing of motion cues was tested with computer animation sequences known as random-dot cinematograms, which resemble the stimuli used to define motion processing deficits in primates with lesions of cortical area MT. Results showed that participants with Alzheimer's disease required significantly greater thresholds for perceiving shapes defined by motion cues compared with participants without dementia (P = 0.0005). There were no significant differences between the two groups (P < 0.05) in static visual acuity, static spatial contrast sensitivity and, surprisingly, dynamic visual acuity, which was normal, and motion direction discrimination, which was relatively spared. We conclude that mild to moderate Alzheimer's disease has significant effects on the perception of structure from motion with relative sparing of motion direction discrimination. We cannot exclude a contribution by retinal pathology, but retinal dysfunction alone cannot explain the pattern of defects we observed. The complex motion image processing deficit we identified is likely to have a cerebral basis and has the potential to affect navigation and the recognition of objects in relative motion, as encountered during walking and automobile driving.
阿尔茨海默病是老年人认知功能异常衰退的最常见原因，且通常会影响视觉功能。最近有证据表明，阿尔茨海默病会损害视觉运动处理能力，但这些结论是基于少数研究案例中相互矛盾的结果得出的，而且复杂运动图像的处理尚未得到研究。在本项关于阿尔茨海默病运动处理的研究中，我们评估了63名成年人的视觉功能：41名患有轻度至中度阿尔茨海默病（平均年龄72.3岁），22名无痴呆症（平均年龄71.7岁）。使用被称为随机点电影图的计算机动画序列测试运动线索的处理能力，该序列类似于用于定义患有大脑皮层MT区损伤的灵长类动物运动处理缺陷的刺激物。结果显示，与无痴呆症的参与者相比，患有阿尔茨海默病的参与者感知由运动线索定义的形状所需的阈值显著更高（P = 0.0005）。两组在静态视力、静态空间对比敏感度方面，以及令人惊讶的是在正常的动态视力和相对保留的运动方向辨别能力方面均无显著差异（P < 0.05）。我们得出结论，轻度至中度阿尔茨海默病对从运动中感知结构有显著影响，而运动方向辨别能力相对保留。我们不能排除视网膜病变的影响，但仅视网膜功能障碍无法解释我们观察到的缺陷模式。我们所确定的复杂运动图像处理缺陷可能有大脑基础，并且有可能影响导航以及对行走和汽车驾驶过程中遇到的相对运动物体的识别。
