Human Vision and Eye Movement Laboratory, Department of Ophthalmology and Visual Science, University of British Columbia, Vancouver, BC, Canada.
Neuropsychologia. 2012 May;50(6):1190-201. doi: 10.1016/j.neuropsychologia.2011.11.010. Epub 2011 Nov 19.
Whether an attentional gradient favouring the ipsilesional side is responsible for the line bisection errors in visual neglect is uncertain. We explored this by using a conjunction-search task on the right side of a computer screen to bias attention while healthy subjects performed line bisection. The first experiment used a probe detection task to confirm that the conjunction-search task created a rightward attentional gradient, as manifest in response times, detection rates, and fixation patterns. In the second experiment subjects performed line bisection with or without a simultaneous conjunction-search task. Fixation patterns in the latter condition were biased rightwards as in visual neglect, and bisection also showed a rightward bias, though modest. A third experiment using the probe detection task again showed that the attentional gradient induced by the conjunction-search task was reduced when subjects also performed line bisection, perhaps explaining the modest effects on bisection bias. Finally, an experiment with briefly viewed pre-bisected lines produced similar results, showing that the small size of the bisection bias was not due to an unlimited view allowing deployment of attentional resources to counteract the conjunction-search task's attentional gradient. These results show that an attentional gradient induced in healthy subjects can produce visual neglect-like visual scanning and a rightward shift of perceived line midpoint, but the modest size of this shift points to limitations of this physiological model in simulating the pathologic effects of visual neglect.
是否存在偏向优势侧的注意梯度是导致视觉忽略中线偏误的原因尚不确定。我们通过在电脑屏幕右侧使用合取搜索任务来探索这个问题，以偏向注意，同时让健康受试者进行中线偏误任务。第一个实验使用探测检测任务来确认合取搜索任务创建了一个向右的注意梯度，表现在反应时间、检测率和注视模式上。在第二个实验中，受试者在有或没有同时进行合取搜索任务的情况下进行中线偏误任务。在后者的条件下，注视模式向右偏斜，就像视觉忽略一样，而且偏误也向右偏斜，尽管幅度较小。第三个实验再次使用探测检测任务表明，当受试者同时进行中线偏误任务时，合取搜索任务引起的注意梯度会减小，这可能解释了对线偏斜的适度影响。最后，一个短暂查看预偏斜线的实验产生了类似的结果，表明偏误幅度较小不是因为可以无限查看，从而允许部署注意资源来抵消合取搜索任务的注意梯度。这些结果表明，在健康受试者中诱导的注意梯度可以产生类似于视觉忽略的视觉扫描和感知中线中点的向右移位，但这种移位的适度幅度表明这种生理模型在模拟视觉忽略的病理效应方面存在局限性。
