Ishiai S, Furukawa T, Tsukagoshi H
Department of Neurology, Faculty of Medicine, Tokyo Medical and Dental University, Japan.
Brain. 1989 Dec;112 ( Pt 6):1485-502. doi: 10.1093/brain/112.6.1485.
Patients with unilateral spatial neglect fail to report or respond to stimuli contralateral to the lesion which usually involves the right parietal lobe. When asked to mark the centre of a horizontal line, these patients place the mark to the right of the true midpoint. It has been considered that they neglect the left part of the line and bisect the perceived line segment. We investigated the eye-fixation patterns of hemianopic patients with or without unilateral spatial neglect during the bisection of lines, using an eye camera. Hemianopic patients without unilateral spatial neglect saw the whole lines, searching to the endpoint on the hemianopic side, and bisected it correctly. In contrast, left hemianopics with unilateral spatial neglect never searched to the left hemianopic side. Once they fixated a certain point on the right part of the line, they persisted with this point and marked the subjective midpoint there. Taking left homonymous hemianopia into account, the subjective midpoint appeared to be marked, not at the centre of the line segment perceived in the seeing right visual field, but at the leftmost point of it. However, they could appreciate the deviation of the subjective midpoint in the right visual field when forced to fixate the left endpoint of the line. These findings suggest that the left hemisphere has the ability to estimate the midpoint of the line through the right visual field and that visuospatial disorder in the line bisection test is attributable to the pathological change in the right hemisphere. The results are interpreted to mean that left hemianopic patients with unilateral spatial neglect see a totalized image of a line extending equally to either side of the point where they are going to mark the subjective midpoint. We considered that the right hemisphere completes the line, using the visual input relating to the right part of the line perceived by the left hemisphere.
患有单侧空间忽视的患者无法报告或对病变对侧的刺激做出反应，病变通常累及右侧顶叶。当被要求标记一条水平线的中心时，这些患者会将标记置于真正中点的右侧。人们认为他们忽视了线的左侧部分，并将所感知的线段二等分。我们使用眼动摄像头研究了有或没有单侧空间忽视的偏盲患者在二等分线过程中的眼动注视模式。没有单侧空间忽视的偏盲患者看到了整条线，会看向偏盲侧的端点，并正确地将其二等分。相比之下，患有单侧空间忽视的左侧偏盲患者从不看向左侧偏盲侧。一旦他们注视在线条右侧的某个点上，就会一直停留在这个点上，并在那里标记主观中点。考虑到左侧同向性偏盲，主观中点似乎不是标记在右侧可见视野中所感知线段的中心，而是标记在其最左侧的点上。然而，当被迫注视线的左端点时，他们能够意识到右侧视野中主观中点的偏差。这些发现表明，左半球有能力通过右侧视野估计线的中点，并且在二等分线测试中的视觉空间障碍可归因于右半球的病理变化。结果被解释为意味着患有单侧空间忽视的左侧偏盲患者看到了一条线的整体图像，该线向他们将要标记主观中点的点的两侧等长延伸。我们认为，右半球利用与左半球所感知的线的右侧部分相关的视觉输入来完成这条线。
