Suzuki Kyoko
Department of Behavioral Neurology and Cognitive Neuroscience, Tohoku University Graduate School of Medicine, 2-1 Seiryo-machi, Aoba-ku, Sendai 980-8575, Japan.
No To Shinkei. 2007 Jan;59(1):23-30.
Visual experience depends critically on visual attention, which selects a particular aspect of a visual display. Recent clinical, neuroimaging, and animal studies revealed that visual attention was divided into active and passive or top-down and bottom-up attention. Although these dichotomies are clear-cut in definition, visual attention could be modulated by many factors. Detailed observation of brain-injured patients provides with evidence for dynamic and fine control of visual attention. We observed patients with dorsal simultanagnosia and that with callosal disconnection syndrome. Patients with dorsal simultanagnosia demonstrated that extent of visual attention was dynamically changed depending on the level of visual processing. Despite the ability to read a kanji character and to describe its components correctly, a patient could not notice a component that he had just written and could not assemble individual components to make up a correct kanji character. He could point to an overlapping area of two figures. But once he started to color the overlapping area, he missed the margin of the area and colored much larger area. Another patient with dorsal simultanagnosia missed borderlines between columns of a newspaper and read letters continuously across columns. In contrast, he could point to lines between figures or meaningless patterns easily. These findings indicated that visual attention was directed automatically to meaningful characters. A patients with callosal disconnection syndrome demonstrated left unilateral spatial neglect only when he used his right hand to draw figures. Right hand movement, controlled by the left hemisphere, elicited visual attention to the right hemispace, resulting in the left unilateral spatial neglect. Thus visual attention is not simply top-down or bottom up, but is implicitly affected by the visual recognition as well as motor component of the task.
视觉体验严重依赖于视觉注意力，它会选择视觉显示的特定方面。最近的临床、神经影像学和动物研究表明，视觉注意力可分为主动和被动或自上而下和自下而上的注意力。尽管这些二分法在定义上很明确，但视觉注意力可能会受到多种因素的调节。对脑损伤患者的详细观察为视觉注意力的动态精细控制提供了证据。我们观察了患有背侧同时失认症和胼胝体离断综合征的患者。患有背侧同时失认症的患者表明，视觉注意力的范围会根据视觉处理水平而动态变化。尽管有能力阅读一个汉字并正确描述其组成部分，但一名患者却注意不到自己刚写的一个组成部分，也无法将各个组成部分组合成一个正确的汉字。他可以指出两个图形的重叠区域。但一旦他开始给重叠区域上色，他就会错过该区域的边缘，从而给大得多的区域上色。另一名患有背侧同时失认症的患者错过了报纸栏之间的边界，连续跨栏阅读字母。相比之下，他可以轻松地指出图形之间的线条或无意义的图案。这些发现表明，视觉注意力会自动指向有意义的字符。一名患有胼胝体离断综合征的患者只有在用右手画图时才表现出左侧单侧空间忽视。由左半球控制的右手运动引发了对右半空间的视觉注意力，导致了左侧单侧空间忽视。因此，视觉注意力并非简单的自上而下或自下而上，而是会受到任务的视觉识别以及运动成分的隐性影响。
