EEG neural oscillatory dynamics reveal semantic and response conflict at difference levels of conflict awareness

Jun Jiang, Qinglin Zhang, Simon Van Gaal
2015 Scientific Reports  
Although previous work has shown that conflict can be detected in the absence of awareness, it is unknown how different sources of conflict (i.e., semantic, response) are processed in the human brain and whether these processes are differently modulated by conflict awareness. To explore this issue, we extracted oscillatory power dynamics from electroencephalographic (EEG) data recorded while human participants performed a modified version of the Stroop task. Crucially, in this task conflict
more » ... eness was manipulated by masking a conflict-inducing color word preceding a color patch target. We isolated semantic from response conflict by introducing four color words/patches, of which two were matched to the same response. We observed that both semantic as well as response conflict were associated with mid-frontal theta-band and parietal alpha-band power modulations, irrespective of the level of conflict awareness (high vs. low), although awareness of conflict increased these conflict-related power dynamics. These results show that both semantic and response conflict can be processed in the human brain and suggest that the neural oscillatory mechanisms in EEG reflect mainly "domain general" conflict processing mechanisms, instead of conflict source specific effects. Accumulating evidence shows that many cognitive and perceptual functions can be influenced by unconscious information 1-3 . However, at the same time, research has shown that awareness of information strongly modulates the extent to which participants can use this information for decision-making and complex behavior 4-7 . In this paper, we will focus on the role of awareness in a cognitive control process called "conflict detection". Overall, conflict can arise from several sources, including sensory and motor representations and resolving conflict to optimize behavior is a core cognitive control function 8-10 . By combining a modified version of the Stroop task with oscillatory power analyses on electroencephalographic (EEG) data we aimed to test two specific questions: 1) To what degree is conflict control implemented by domain general or domain specific neural (oscillatory) mechanisms, and 2) to what extent are neural oscillatory processes related to the different forms of conflict processing (sensory and motor) modulated by conflict awareness. Using various versions of the masked priming tasks, previous studies have revealed that prime-induced conflict can affect the speed and accuracy of behavioral responses and neural modulations related to conflict can be detected in the absence of awareness 3,11-16 . In a typical conflict experiment, participants are required to perform a speeded two-choice response to a target stimulus that can be preceded by a so-called prime stimulus. For example, in a Stroop priming task, a modified version of the classic Stroop
doi:10.1038/srep12008 pmid:26169473 pmcid:PMC4500944 fatcat:7cjdcxw2gzexpm42qqsqzr2evq