One possible pathological mechanism underlying the rightward bisection error of right-brain-damaged patients with left spatial neglect is a leftward relaxation of the spatial representational medium. This view was originally based on the finding that patients with left neglect, required to extend horizontal segments, in order to double their original length, may exhibit a relative left overextension of the drawn lines (Bisiach et al., 1994). We investigated this putative distortion of representational space using a 16 cm 'line segmentation' task (Experiment I). Were the representation of space relaxed contralesionally, a progressive increase from right to left of the size of the drawn segments would be expected. Right-brain-damaged patients with left unilateral neglect (N=12) performed the segmentation task with no left versus right differences, as right-brain-damaged patients without neglect (N=8), and neurologically unimpaired control subjects (N=10), did. Experiments 2 and 3 explored the effects of sample length (1, 2, 4, and 8cm), by which the 16cm lines had to be segmented. Neglect patients produced longer left-sided segments only for the 8 cm sample (i.e. half of the length of the segment). This set of experiments suggests an impairment in the segmentation task only with the larger (8 cm) sample, when a more global level of processing may be involved. Experiment 4 assessed this hypothesis by a 'part/whole' bisection task, using 8 cm lines, presented either embedded in a longer 16 cm line or in isolation. Neglect patients made a larger rightward bisection error when the segment was not embedded. The suggestion is made that the lateral distortion of the representation of space in neglect patients (i.e., a leftward relaxation of the spatial medium) concerns tasks where a more 'global' representation of the visual stimulus has to be set up. The different demands of the segmentation and bisection tasks are discussed.

中文翻译：

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当整体大于部分的总和时：来自视觉空间忽略的证据。

左脑受损的右脑损伤患者的右等分误差的一种可能的病理机制是空间表征介质的向左松弛。该观点最初是基于以下发现：需要将水平线段延伸以使其原始长度加倍的左忽视患者可能表现出画线的相对左过度伸展（Bisiach等，1994）。我们使用16厘米的“线分割”任务（实验I）调查了这种表示空间的推定失真。如果空间上的表示相反，则预期绘制段的大小从右到左逐渐增加。左脑单侧忽视的右脑损伤患者（N = 12）进行分割任务，没有左右差异，就像右脑受损的患者没有忽视（N = 8）和神经系统无障碍的对照受试者（N = 10） ），做了。实验2和3探索了样本长度（1、2、4和8cm）的影响，必须将样本分割为16cm的线。被忽视的患者仅针对8 cm的样本（即该段长度的一半）产生了较长的左侧段。这组实验表明，只有在较大（8厘米）的样本中才可能进行分割，这可能会涉及到更高的整体处理水平。实验4使用8 cm线通过“部分/整个”等分任务评估了该假设，该线嵌入更长的16 cm线中或单独出现。如果未嵌入该节段，则忽略患者的右向平分误差会更大。提出的建议是，被忽视患者的空间表征的横向失真（即空间介质的向左松弛）与必须建立视觉刺激的“整体”表征的任务有关。讨论了分割和二等分任务的不同需求。