Mathes Birgit, Trenner Dennis, Fahle Manfred
University of Bremen, Department of Human Neurobiology, Argonnenstr. 3, 28211 Bremen, Germany.
Brain Res. 2006 Oct 9;1114(1):98-112. doi: 10.1016/j.brainres.2006.07.068. Epub 2006 Aug 30.
Psychophysical studies demonstrated under which task conditions contour integration based on orientation cues succeeds or fails. We investigated how the electrophysiological correlate of contour integration is modulated by changes in task demands. In two experiments, event-related potentials (ERPs) were recorded. We presented open or nearly closed contours defined by Gabor elements embedded in a background of randomly oriented distracters. In experiment 1, randomly oriented Gabors preceded the test stimulus, while in experiment 2, the screen was blank before appearance of the test stimulus. Correct performance was above 96% for aligned and slightly misaligned contours but did not significantly differ from chance level for random orientations of the contour elements. Detectable contours elicited a negative shift over posterior recording sites. This effect started about 150 ms after stimulus onset but was delayed for more difficult contour integration. Presenting the stimulus after a random display elicited a frontal selection positivity (FSP). In both experiments, contours elicited a P3, which was larger for aligned compared to misaligned contours. Timing, duration and localisation of the negative enhancement were similar to both the texture segmentation VEP (tsVEP) and the selection negativity (SN). Our results indicate that contours are processed similar to textures and that decreasing saliency of detectable contours is compensated by increasing processing time which possibly results from increasing allocation of visual selective attention.
心理物理学研究表明，在何种任务条件下基于方向线索的轮廓整合会成功或失败。我们研究了轮廓整合的电生理相关性如何受任务需求变化的调节。在两个实验中，记录了事件相关电位（ERP）。我们呈现了由嵌入随机方向干扰物背景中的Gabor元素定义的开放或接近闭合的轮廓。在实验1中，随机方向的Gabor元素先于测试刺激出现，而在实验2中，测试刺激出现之前屏幕是空白的。对齐和轻微错位轮廓的正确表现高于96%，但轮廓元素随机方向的表现与随机水平无显著差异。可检测到的轮廓在后部记录部位引发负向偏移。这种效应在刺激开始后约150毫秒开始，但对于更困难的轮廓整合会延迟。在随机显示后呈现刺激会引发额叶选择正波（FSP）。在两个实验中，轮廓都引发了P3，对齐轮廓的P3比错位轮廓的更大。负向增强的时间、持续时间和定位与纹理分割视觉诱发电位（tsVEP）和选择负波（SN）相似。我们的结果表明，轮廓的处理方式与纹理相似，可检测轮廓显著性的降低通过增加处理时间来补偿，这可能是由于视觉选择性注意分配增加所致。
