Khoe W, Freeman E, Woldorff M G, Mangun G R
Department of Neurosciences, University of California, San Diego, La Jolla, CA 92093-0608, USA.
Brain Res. 2006 Mar 17;1078(1):101-11. doi: 10.1016/j.brainres.2005.12.083. Epub 2006 Feb 28.
Freeman et al. demonstrated that detection sensitivity for a low contrast Gabor stimulus improved in the presence of flanking, collinearly oriented grating stimuli, but only when observers attended to them. By recording visual event-related potentials (ERPs) elicited by a Gabor stimulus, we investigated whether this contextual cueing effect involves changes in the short-latency afferent visual signal from V1 that have a stimulus onset latency between 60 and 80 ms and/or longer-latency changes from visual cortex. Under dual-task conditions, the subjects performed contrast discrimination for a central Gabor and an orientation judgment for a pre-specified subset of the flanking Gabors. On random trials, the central Gabor could be collinearly or orthogonally oriented with respect to the attended flankers. Subjects showed improvements in discriminating the contrast of the central grating when it was oriented collinearly with the attended flankers. The ERP difference between attending to collinear versus orthogonal flankers manifested as a positive polarity response at occipital electrodes with a latency of 180-250 ms after stimulus onset. No shorter-latency contextual cueing differences were observed in the ERPs. The ERP latency profile of the contextual cueing effect argues against the hypothesis that short-latency afferent activity from V1 is the stage of processing at which attention can influence neuronal lateral interactions. However, the scalp voltage distribution of the longer-latency contextual cueing effect is similar to the one generated by the early phasic stimulus onset activity from V1. These findings leave open the possibility that V1 is involved in the attentional modulation of lateral interactions but that this has a longer time course, likely being mediated by re-afferent inputs from later stages of the visual pathway.
弗里曼等人证明，在存在侧翼共线定向光栅刺激的情况下，低对比度加博尔刺激的检测灵敏度会提高，但前提是观察者关注这些刺激。通过记录由加博尔刺激引发的视觉事件相关电位（ERP），我们研究了这种上下文线索效应是否涉及来自V1的短潜伏期传入视觉信号的变化（其刺激起始潜伏期在60至80毫秒之间）和/或来自视觉皮层的长潜伏期变化。在双任务条件下，受试者对中央加博尔进行对比度辨别，并对侧翼加博尔的预先指定子集进行方向判断。在随机试验中，中央加博尔可以与被关注的侧翼共线或正交定向。当中央光栅与被关注的侧翼共线定向时，受试者在辨别其对比度方面表现出改善。关注共线侧翼与正交侧翼时的ERP差异表现为刺激开始后180 - 250毫秒时枕叶电极处的正极性反应。在ERP中未观察到更短潜伏期的上下文线索差异。上下文线索效应的ERP潜伏期特征与以下假设相悖：来自V1的短潜伏期传入活动是注意力可以影响神经元侧向相互作用的加工阶段。然而，长潜伏期上下文线索效应的头皮电压分布与由V1的早期相位刺激起始活动产生的分布相似。这些发现留下了一种可能性，即V1参与了侧向相互作用的注意力调节，但这具有更长的时间进程，可能由视觉通路后期阶段的再传入输入介导。
