Kotchoubey B, Wascher E, Verleger R
Department of Neurology, Medical University of Lübeck, Germany.
Biol Psychol. 1997 Jun 20;46(1):25-50. doi: 10.1016/s0301-0511(96)05236-2.
In two experiments, large letters H or Z composed of small letters (also H or Z) were presented. Subjects had to make a two-choice motor response (e.g. H--left key, Z--right key). A cue presented 500 ms before the letter indicated which level (global or local) was relevant. In Experiment I, a third letter (T) sometimes appeared either at the cued or the non-cued level; in the former case, subjects had to shift their attention and to respond to stimulus features located at the non-cued level. The interference effect (RT delay in response to incongruent stimuli as compared to congruent ones) was larger when the local, rather than global, level was cued. A slow anterior negativity preceding globally-cued stimuli and shorter N1 and P2 ERP component latencies to these stimuli indicated better preparation for processing of global, as compared to local, stimulus features. The shift from local to global focus yielded a larger increase of RT, error rate, and of the P600 latency than the global-to-local shift. The P600 latency changes were parallel to those of RT. In Experiment II, the attentional shift was provoked by stimulus color red-colored letters meant that the cue was invalid, and thus, subjects had to respond to the non-cued level. Neither the interference nor the attentional shift demonstrated any asymmetry between the global and local levels. ERPs also did not differ substantially after local and global cues. In the condition demanding a shift of focus (invalid cue, incongruent letter), a positive deflection of the lateralized readiness potential indicated the activation of the wrong response channel. The large RT increment in this condition was not accompanied by an increase of the P600 latency. Two possible mechanisms of attentional shift may be proposed, the first related to perceptual processes (e.g. an additional visual search), and the second, to the competition between two response intentions.
在两个实验中，呈现由小写字母（也是H或Z）组成的大写字母H或Z。受试者必须做出二选一的运动反应（例如，H——左键，Z——右键）。在字母出现前500毫秒呈现的一个提示表明哪个水平（整体或局部）是相关的。在实验一中，第三个字母（T）有时会出现在提示的或未提示的水平；在前一种情况下，受试者必须转移注意力并对位于未提示水平的刺激特征做出反应。当提示的是局部而非整体水平时，干扰效应（与一致刺激相比，对不一致刺激的反应时延迟）更大。与局部刺激特征相比，在整体提示刺激之前出现的缓慢前部负波以及这些刺激的N1和P2 ERP成分潜伏期较短，表明对整体刺激特征的处理有更好的准备。从局部焦点转移到整体焦点所产生 的反应时、错误率和P600潜伏期的增加，比从整体焦点转移到局部焦点时更大。P600潜伏期的变化与反应时的变化平行。在实验二中，注意力转移是由刺激颜色引发的——红色字母意味着提示无效，因此，受试者必须对未提示的水平做出反应。干扰和注意力转移在整体和局部水平之间均未表现出任何不对称性。在局部和整体提示后，ERP也没有实质性差异。在需要焦点转移的条件下（无效提示，不一致字母），侧化准备电位的正向偏转表明错误反应通道被激活。在这种情况下，反应时的大幅增加并没有伴随着P600潜伏期的增加。可以提出两种注意力转移的可能机制，第一种与感知过程有关（例如额外的视觉搜索），第二种与两种反应意图之间的竞争有关。
