Brain in Action Laboratory, Department of Kinesiology and Physical Education, University of Lethbridge , Lethbridge, AB , Canada.
Front Neurol. 2014 Jan 22;5:4. doi: 10.3389/fneur.2014.00004. eCollection 2014.
Hemispatial neglect is a common outcome of stroke that is characterized by the inability to orient toward, and attend to stimuli in contralesional space. It is established that hemispatial neglect has a perceptual component, however, the presence and severity of motor impairments is controversial. Establishing the nature of space use and spatial biases during visually guided actions amongst healthy individuals is critical to understanding the presence of visuomotor deficits in patients with neglect. Accordingly, three experiments were conducted to investigate the effect of object spatial location on patterns of grasping. Experiment 1 required right-handed participants to reach and grasp for blocks in order to construct 3D models. The blocks were scattered on a tabletop divided into equal size quadrants: left near, left far, right near, and right far. Identical sets of building blocks were available in each quadrant. Space use was dynamic, with participants initially grasping blocks from right near space and tending to "neglect" left far space until the final stages of the task. Experiment 2 repeated the protocol with left-handed participants. Remarkably, left-handed participants displayed a similar pattern of space use to right-handed participants. In Experiment 3 eye movements were examined to investigate whether "neglect" for grasping in left far reachable space had its origins in attentional biases. It was found that patterns of eye movements mirrored patterns of reach-to-grasp movements. We conclude that there are spatial biases during visually guided grasping, specifically, a tendency to neglect left far reachable space, and that this "neglect" is attentional in origin. The results raise the possibility that visuomotor impairments reported among patients with right hemisphere lesions when working in contralesional space may result in part from this inherent tendency to "neglect" left far space irrespective of the presence of unilateral visuospatial neglect.
偏侧空间忽略是中风的常见后果，其特征是无法朝向对侧空间的刺激，并对其进行注意。已经确定偏侧空间忽略具有知觉成分，然而，运动损伤的存在和严重程度存在争议。在健康个体中，在视觉引导的动作中确定空间使用和空间偏差的性质对于理解忽略患者的视动缺陷的存在至关重要。因此，进行了三项实验来研究物体空间位置对抓握模式的影响。实验 1 要求右利手参与者伸手去抓取放在桌上的积木，以构建 3D 模型。积木分散在等分的四个象限的桌面上：左近、左远、右近和右远。每个象限都有相同的积木套件。空间使用是动态的，参与者最初从右近空间抓取积木，并倾向于“忽略”左远空间，直到任务的最后阶段。实验 2 让左利手参与者重复了该方案。值得注意的是，左利手参与者表现出与右利手参与者相似的空间使用模式。在实验 3 中，研究了眼球运动，以探讨对左远可触及空间的抓握“忽略”是否源于注意力偏向。结果发现，眼球运动模式与伸手抓握运动模式相匹配。我们得出的结论是，在视觉引导的抓握过程中存在空间偏差，特别是有一种忽略左远可触及空间的倾向，并且这种“忽略”是源于注意力的。结果表明，报告称在对侧空间中工作的右侧大脑损伤患者存在视动障碍，部分原因可能是这种固有的“忽略”左远空间的倾向，而与单侧视空间忽略的存在无关。
