Sheu Yi-Shin, Courtney Susan M
Department of Psychological & Brain Sciences, Johns Hopkins University, Baltimore, MD, USA.
Department of Psychological & Brain Sciences, Johns Hopkins University, Baltimore, MD, USA; F.M. Kirby Research Center for Functional Brain Imaging, The Kennedy Krieger Institute, Baltimore, MD, USA; Department of Neuroscience, Johns Hopkins University, Baltimore, MD, USA.
Cortex. 2016 Dec;85:13-24. doi: 10.1016/j.cortex.2016.09.018. Epub 2016 Oct 1.
Conflict between multiple sensory stimuli or potential motor responses is thought to be resolved via bias signals from prefrontal cortex (PFC). However, population codes in the PFC also represent abstract information, such as task rules. How is conflict between active abstract representations resolved? We used functional neuroimaging to investigate the mechanism responsible for resolving conflict between abstract representations of task rules. Participants performed two different tasks based on a cue. We manipulated the degree of conflict at the task-rule level by training participants to associate the color and shape dimensions of the cue with either the same task rule (congruent cues) or different ones (incongruent cues). Phonological and semantic tasks were used in which performance depended on learned, abstract representations of information, rather than sensory features of the target stimulus or on any habituated stimulus-response associations. In addition, these tasks activate distinct regions that allowed us to measure magnitude of conflict between tasks. We found that incongruent cues were associated with increased activity in several cognitive control areas, including the inferior frontal gyrus, inferior parietal lobule, insula, and subcortical regions. Conflict between abstract representations appears to be resolved by rule-specific activity in the inferior frontal gyrus that is correlated with enhanced activity related to the relevant information. Furthermore, multi-voxel pattern analysis of the activity in the inferior frontal gyrus was shown to carry information about both the currently relevant rule (semantic/phonological) and the currently relevant cue context (color/shape). Similar to models of attentional selection of conflicting sensory or motor representations, the current findings indicate part of the frontal cortex provides a bias signal, representing task rules, that enhances task-relevant information. However, the frontal cortex can also be the target of these bias signals in order to enhance abstract representations that are independent of particular stimuli or motor responses.
多种感觉刺激或潜在运动反应之间的冲突被认为是通过前额叶皮层(PFC)发出的偏向信号来解决的。然而,PFC中的群体编码也代表抽象信息,比如任务规则。活跃的抽象表征之间的冲突是如何解决的呢?我们使用功能神经成像来研究负责解决任务规则抽象表征之间冲突的机制。参与者根据一个提示执行两项不同的任务。我们通过训练参与者将提示的颜色和形状维度与相同的任务规则(一致提示)或不同的任务规则(不一致提示)相关联,在任务规则层面操纵冲突程度。使用了语音和语义任务,其中表现取决于所学的信息抽象表征,而非目标刺激的感觉特征或任何习惯性的刺激 - 反应关联。此外,这些任务激活了不同的区域,使我们能够测量任务之间冲突的程度。我们发现,不一致提示与几个认知控制区域的活动增加有关,包括额下回、顶下小叶、脑岛和皮层下区域。抽象表征之间的冲突似乎是通过额下回中与相关信息增强活动相关的规则特异性活动来解决的。此外,对额下回活动的多体素模式分析表明,它携带有关当前相关规则(语义/语音)和当前相关提示背景(颜色/形状)的信息。与冲突感觉或运动表征的注意力选择模型类似,当前研究结果表明额叶皮层的一部分提供了一个代表任务规则的偏向信号,该信号增强了与任务相关的信息。然而,额叶皮层也可以是这些偏向信号的目标,以增强独立于特定刺激或运动反应的抽象表征。