Töllner Thomas, Wang Yijun, Makeig Scott, Müller Hermann J, Jung Tzyy-Ping, Gramann Klaus
Department of Experimental Psychology and
Graduate School of Systemic Neurosciences, LMU Munich, D-80802 Munich, Germany.
J Neurosci. 2017 Mar 1;37(9):2504-2515. doi: 10.1523/JNEUROSCI.1752-16.2017. Epub 2017 Jan 30.
One of the most firmly established factors determining the speed of human behavioral responses toward action-critical stimuli is the spatial correspondence between the stimulus and response locations. If both locations match, the time taken for response production is markedly reduced relative to when they mismatch, a phenomenon called the Simon effect. While there is a consensus that this stimulus-response (S-R) conflict is associated with brief (4-7 Hz) frontal midline theta (fmθ) complexes generated in medial frontal cortex, it remains controversial (1) whether there are multiple, simultaneously active theta generator areas in the medial frontal cortex that commonly give rise to conflict-related fmθ complexes; and if so, (2) whether they are all related to the resolution of conflicting task information. Here, we combined mental chronometry with high-density electroencephalographic measures during a Simon-type manual reaching task and used independent component analysis and time-frequency domain statistics on source-level activities to model fmθ sources. During target processing, our results revealed two independent fmθ generators simultaneously active in or near anterior cingulate cortex, only one of them reflecting the correspondence between current and previous S-R locations. However, this fmθ response is not exclusively linked to conflict but also to other, conflict-independent processes associated with response slowing. These results paint a detailed picture regarding the oscillatory correlates of conflict processing in Simon tasks, and challenge the prevalent notion that fmθ complexes induced by conflicting task information represent a unitary phenomenon related to cognitive control, which governs conflict processing across various types of response-override tasks. Humans constantly monitor their environment for and adjust their cognitive control settings in response to conflicts, an ability that arguably paves the way for survival in ever-changing situations. Anterior cingulate-generated frontal midline theta (fmθ) complexes have been hypothesized to play a role in this conflict-monitoring function. However, it remains a point of contention whether fmθ complexes govern conflict processing in a unitary, paradigm-nonspecific manner. Here, we identified two independent fmθ oscillations triggered during a Simon-type task, only one of them reflecting current and previous conflicts. Importantly, this signal differed in various respects (cortical origin, intertrial history) from fmθ phenomena in other response-override tasks, challenging the prevalent notion of conflict-induced fmθ as a unitary phenomenon associated with the resolution of conflict.
决定人类对行动关键刺激做出行为反应速度的最确定因素之一是刺激位置与反应位置之间的空间对应关系。如果两者位置匹配，相对于不匹配时，产生反应所需的时间会显著减少，这一现象称为西蒙效应。虽然人们一致认为这种刺激-反应（S-R）冲突与内侧前额叶皮质中产生的短暂（4-7赫兹）额中线θ波（fmθ）复合体有关，但仍存在争议：（1）内侧前额叶皮质中是否存在多个同时活跃的θ波发生器区域，这些区域通常会产生与冲突相关的fmθ复合体；如果是这样，（2）它们是否都与冲突任务信息的解决有关。在这里，我们在西蒙型手动伸手任务中结合了心理计时法和高密度脑电图测量，并对源水平活动进行独立成分分析和时频域统计以模拟fmθ源。在目标处理过程中，我们的结果显示两个独立的fmθ发生器在前扣带回皮质内或附近同时活跃，其中只有一个反映当前和先前S-R位置之间的对应关系。然而，这种fmθ反应并非仅与冲突相关，还与其他与反应减慢相关的、与冲突无关的过程有关。这些结果描绘了西蒙任务中冲突处理的振荡相关性的详细图景，并挑战了普遍观点，即由冲突任务信息诱发的fmθ复合体代表与认知控制相关的单一现象，认知控制支配着各种类型的反应优先任务中的冲突处理。人类不断监测周围环境并根据冲突调整认知控制设置，这种能力可以说是在不断变化的情况下生存的关键。前扣带回产生的额中线θ波（fmθ）复合体被认为在这种冲突监测功能中发挥作用。然而，fmθ复合体是否以单一的、范式非特异性的方式支配冲突处理仍存在争议。在这里，我们在西蒙型任务中识别出两个独立的fmθ振荡，其中只有一个反映当前和先前的冲突。重要的是，该信号在多个方面（皮质起源、试验间历史）与其他反应优先任务中的fmθ现象不同，挑战了将冲突诱发的fmθ视为与冲突解决相关的单一现象的普遍观点。
