Karnath H O, Schenkel P, Fischer B
Department of Neurology, University of Freiburg, Germany.
Brain. 1991 Aug;114 ( Pt 4):1997-2014. doi: 10.1093/brain/114.4.1997.
The present study examines which egocentric coordinate system determines the border between the disturbed 'contralateral' and the normal 'ipsilateral' side in patients with hemineglect. Based on the observation of significantly longer reaction times for saccades towards stimuli presented in the left visual field (LVF) in right brain-damaged patients with hemineglect, stimuli were presented randomly to the LVF or RVF and the corresponding saccadic reaction times (SRTs) were compared. Beginning with the standard body position generally used for the investigation of neglect patients, where the midlines of head, trunk and visual field are parallel and oriented straight towards the middle of the projection screen, the spatial relation between orientation of head and trunk midlines and location of the target stimuli was systematically varied while holding the retinal projection of the stimuli constant. The deficit in SRTs towards the LVF in 4 right brain-damaged patients with left-sided hemineglect could be compensated for by turning the patients' trunk to the left, such that both LVF and RVF-stimuli were projected to the right, ipsilateral side of trunk space. The results suggest that the spatial orientation of the trunk midline divides our normal perception of space into an egocentric 'left' and an egocentric 'right' sector and seems to be the decisive factor for determining the neglected 'contralateral' part of space in patients with brain-damage. They indicate that the trunk midline constitutes the physical anchor for calculation of the internal egocentric coordinate frame for representing body position with respect to external objects. The hypothesis of Ventre et al. (1984) that deficient reactions to contralaterally located stimuli in neglect patients could be the result of a displacement of these egocentric coordinates towards the non-neglected, ipsilateral side is discussed.
本研究探讨了在半侧空间忽视患者中，哪种自我中心坐标系决定了受干扰的“对侧”和正常的“同侧”之间的边界。基于对右侧脑损伤伴半侧空间忽视患者向左视野（LVF）呈现的刺激进行扫视时反应时间明显更长的观察，刺激随机呈现于LVF或右视野（RVF），并比较相应的扫视反应时间（SRT）。从通常用于研究忽视患者的标准身体姿势开始，即头部、躯干和视野的中线平行且直接朝向投影屏幕的中间，在保持刺激的视网膜投影不变的同时，系统地改变头部和躯干中线的方向与目标刺激位置之间的空间关系。4例左侧半侧空间忽视的右侧脑损伤患者对LVF刺激的SRT缺陷可通过将患者躯干向左转动来弥补，这样LVF和RVF刺激都投射到躯干空间的右侧，即同侧。结果表明，躯干中线的空间方向将我们对空间的正常感知分为以自我为中心的“左”和“右”两个部分，并且似乎是确定脑损伤患者被忽视的空间“对侧”部分的决定性因素。它们表明，躯干中线构成了用于计算以自我为中心的内部坐标框架的物理锚点，该坐标框架用于表示身体相对于外部物体的位置。文中还讨论了Ventre等人（1984年）的假设，即忽视患者对位于对侧的刺激反应不足可能是这些自我中心坐标向未被忽视的同侧偏移的结果。
