Stimulus context in hemineglect.
Stimulus context in hemineglect.
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偏侧忽视的刺激环境。
DOI：
10.1093/brain/121.10.2003
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发表时间：
1998
期刊：
影响因子：
--
通讯作者：
Sharma,R
中科院分区：
文献类型：
--
作者：
Marshall,RS;Lazar,RM;Krakauer,JW;Sharma,R
在右脑损伤和左半脑切除的患者中，水平线向右偏是很好的描述。由于观察到半切患者可能会将非常短的线平分到真正中点的左侧(所谓的交叉效应)，已经提出了更多的模型来将这一发现合并到现有的半切理论中。我们调查了6名左半身切除患者的线长效应。当呈现任意一组相同(参考)长度的线条时，不同线条长度的线条平分上的向右偏差百分比保持恒定。当第二长度的线被混合成任何一组均匀的线时，参考线上的对分性能改变。如果添加的线比参考线短，则参照线的感知中点向右移动；如果添加的线较长，则发生左移。向左移动包括跨越真正的中点的移动，再现了交叉效应。在手动线平分任务和不需要人工反应的线平分辨别任务中，感知的中点都发生了移动。我们认为，交叉效应可能是更一般的刺激-语境效应的一部分，在这种效应中，一条线的感知中点与绝对长度无关，而是与这条线相对于呈现它的其他线的长度有关。到目前为止，这种背景效应还没有在忽视综合征中描述过。这种效应的一种可能机制是由焦点刺激和它之前的所有刺激的综合影响产生的长度估计的一般化。
Rightward deviation on bisection of a horizontal line is well described in patients with right brain injury and left hemineglect. Because of the observation that hemineglect patients may bisect very short lines to the left of the true midpoint (the so-called crossover effect), additional models have been proposed to incorporate this finding into existing theories of hemineglect. We investigated a line-length effect in six patients with left hemineglect. When presented with any set of lines of uniform (reference) length, percentage rightward deviation on line bisection remained constant across different line lengths. When lines of a second length were mixed into any uniform set of lines, bisection performance on the reference lines changed. A rightward shift in the perceived midpoint of the reference line occurred if the added lines were shorter than the reference lines; a leftward shift occurred if the added lines were longer. Leftward shifts included shifts across the true midpoint, reproducing the crossover effect. Shifts in the perceived midpoint occurred both on a manual line bisection task and on a line bisection discrimination task in which no manual response was required. We propose that the crossover effect may be part of a more general stimulus-context effect in which the perceived midpoint of a line is related not to absolute length, but to the line's length relative to other lines with which it is presented. Such a context effect has not hitherto been described in the neglect syndrome. A possible mechanism for the effect is a generalization of length estimation produced by the combined influence of the focal stimulus and all stimuli that precede it.