Space exploration in neglect
Space exploration in neglect
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DOI：
10.1093/brain/121.12.2357
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发表时间：
1998-12-01
期刊：
影响因子：
14.5
通讯作者：
Dichgans, J
中科院分区：
文献类型：
--
作者：
Karnath, HO;Niemeier, M;Dichgans, J
本研究调查了被忽视患者在探索周围环境时的凝视、头部和眼睛在头部的运动。在被忽视患者周围的球体的内表面上呈现随机的字母配置，要求自由探索眼睛和头部的运动。受试者被要求搜索一个单一的（不存在的）目标字母。忽视患者的眼睛和头部运动的协调性与通常在健康受试者中观察到的指向偏心视觉目标的模式相似。此外，与健康受试者一样，被忽视的患者也通过凝视探索空间，他们的头部和眼睛的头部运动对称地分布在空间的首选方向上。然而，与对照组相比，这些探索中心向右移动。注视和头部运动的平均水平位置位于身体正中矢状面右侧，眼入头运动的平均水平位置位于头部中线右侧，首选方向远离水平注视、头部和眼入头运动的解剖学极限。因此，对这些方向左右更偏心位置的探查减少不能用解剖学上的限制来解释。研究结果反驳了一种忽视模型，该模型提出了一种向同侧倾斜的注意力梯度。在探索周围环境时，患者没有将目光，头部或头部的眼睛朝向极端的同侧，甚至没有靠近它。结果倾向于一个偏差模型，表明整个框架的探索行为向同侧转移。除了这种转变，我们还发现了忽视中视觉探索改变的第二个组成部分。患者的头部和凝视运动在偏离探索中心周围表现出减少的可变性。变异性不是普遍减少，而是特别关注水平维度。即使两组之间的探索区域是平行的，后者也被发现了，要求对照受试者只搜索被忽视患者自发探索的字母阵列的那一部分。讨论了可能的机制，例如更新视觉目标的空间表示的干扰能力或在水平维度上改变空间的神经表示。
The present study investigated the gaze as well as the head and the eye-in-head movements of neglect patients while they were exploring their surroundings, A random configuration of letters was presented on the inner surface of a sphere that surrounded the subject, requiring free exploratory eye and head movements. The subjects were requested to search for a single (non-existent) target letter. The co-ordination of eye and head movements in patients with neglect resembled the pattern usually observed in healthy subjects orienting to eccentric visual targets. They performed hypometric head movements with additional shifts of eye-in-head position, Moreover, like healthy subjects, the patients with neglect explored space with gaze, with head and eye-in-head movements that were symmetrically distributed around preferred orientations in space, However, in contrast to controls, these centres of exploration were shifted towards the right. The average horizontal position of gaze and of head movements lay right of the body's mid-sagittal plane, the average eye-in-head position right of the head midline, The preferred orientations were located far away from the anatomical limits of horizontal gaze, head and eye-in-head movements. The decrease of exploration towards more eccentric locations left and right of these orientations thus could not be explained by anatomical restrictions. The results argue against a model of neglect that proposes a lateral gradient of attentional orienting towards the ipsilesional side. Exploring the surroundings, the patients did not orient gaze, the head or the eyes in the head towards the extreme ipsilesional side, nor even close to it. The results favour a deviation model suggesting a shift of the whole frame for exploratory behaviour towards the ipsilesional side. In addition to this shift, we found a second component of altered visual exploration in neglect. The patients' head and gaze movements exhibited a reduced variability around the deviated centre of exploration. The variability was not generally reduced but rather concerned specifically the horizontal dimension. The latter was found even when the area of exploration was paralleled between the groups, requiring the control subjects to search only in that part of the letter array that the neglect patients had explored spontaneously. Possible mechanisms, such as a disturbed ability to update the spatial representation of visual targets or an altered neural representation of space in the horizontal dimension, are discussed.