Causes of cross-over in unilateral neglect: between-group comparisons, within-patient dissociations and eye movements
Causes of cross-over in unilateral neglect: between-group comparisons, within-patient dissociations and eye movements
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DOI：
10.1093/brain/awh461
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发表时间：
2005-06-01
期刊：
影响因子：
14.5
通讯作者：
Gasparini, M
中科院分区：
文献类型：
--
作者：
Doricchi, F;Guariglia, P;Gasparini, M
左单侧忽视患者将长水平线平分到真中心的右侧。然而，当给予较短的线条时，许多相同的患者将中点标记在真正中心的左侧，朝向其他被忽视的空间。这种矛盾的现象被称为“交叉”，很难根据目前对忽视综合症的描述来解释。为了探讨交叉的原因，在第一项研究中，我们评估了单侧脑损伤患者中有忽视和偏视、有忽视和无偏视、有偏视和无忽视和无忽视或偏视的20、100和200毫米水平线的平分。20毫米线交叉仅在偏视忽视患者中发现。为了进一步确定视野缺陷对交叉的影响，在第二项研究中，我们比较了两名有对视忽视和下象限视的右脑损伤患者和一名没有忽视的下象限视患者的表现。患者对分定向的线，以便越过或不越过视野的盲象限。当20毫米短线穿过盲象限时，忽视患者出现交叉；当同一条线穿过视觉象限时，交叉是不存在的。这些发现被一名忽视患者的检查证实，右眼对侧左视半球中央5度保留，而左眼没有保留。在单目观察中，与左眼等分20 mm线时出现交叉，与右眼等分时无交叉。眼球运动记录显示，在对分时刻，左眼的注视点移向对分线端点，而右眼的注视点仍固定在对分线中心。长着长长的皱纹，双眼同时偏离。这些结果表明，在被忽视的患者中，只有当长线平分的同色差越过被忽视空间的视障盲区时，短线平分的同色差才会变成明显矛盾的对视平分。交叉似乎依赖于反射性对视目光转移所产生的小空间效应，从而允许视半球偏心注视。在长线平分时，这些影响被同切线段的明显延长所引起的强烈的注意偏差所抵消。这一解释建立了忽视综合症的交叉和当前描述之间的一致性。
Patients with left unilateral neglect bisect long horizontal lines to the right of the true centre. However, when given short lines, many of the same patients mark the midpoint to the left of the true centre, towards the otherwise neglected space. This paradoxical phenomenon has been termed 'cross-over' and is difficult to explain based on current accounts of the neglect syndrome. To explore the causes of cross-over, in a first study we evaluated bisection of 20, 100 and 200 mm horizontal lines in groups of unilateral brain-damaged patients with neglect and hemianopia, with neglect and no hemianopia, with hemianopia and no neglect and without neglect or hemianopia. Cross-over of 20 mm lines was found only in neglect patients with hemianopia. To ascertain further the influence of visual field defects on cross-over, in a second study we compared the performance of two right-brain-damaged patients with contralesional neglect and inferior quadrantanopia with that of a patient with inferior quadrantanopia and no neglect. Patients bisected lines oriented so as to cross or uncross the blind quadrant of the visual field. When short 20 mm lines crossed the blind quadrant, neglect patients showed cross-over; when the same lines crossed the seeing quadrants cross-over was absent. These findings were confirmed by the examination of a neglect patient with sparing of the central 5 degrees of the contralesional left visual hemifield in the right eye and no sparing in the left eye. In monocular viewing, cross-over was present when 20 mm lines were bisected with the left eye and absent when bisected with the right eye. Recording of eye movements showed that at the moment of bisection left eye fixations shifted towards the contralesional line endpoint whereas right eye fixations remained anchored to the centre of the line. With long lines, both eyes deviated ipsilesionally. These results show that in neglect patients ipsilesional deviation in the bisection of long lines turns into apparently paradoxical contralesional bisection of short ones only when these cross a retinotopically blind sector of the neglected space. Cross-over seems to depend on the small spatial effects produced by reflexive contralesional gaze shifts allowing eccentric fixations with the seeing hemifield. During the bisection of long lines, these effects are cancelled out by the strong attentional deviation induced by the marked extension of the ipsilesional line segment. This explanation establishes coherence between cross-over and current accounts of the neglect syndrome.