Linking inter-individual differences in the conflict adaptation effect to spontaneous brain activity Ting Wang a,b , Zhencai Chen a , Guang Zhao a , Glenn Hitchman a , Congcong Liu a , Xiaoyue Zhao a , Yijun Liu a , Antao Chen a, ⁎ a Key laboratory of Cognition and Personality of Ministry of Education, Faculty of Psychology, Southwest University, Chongqing, China b Laboratory of Cognition and Mental Health, Chongqing University of Arts and Sciences, Chongqing, China abstract article info Article history: Accepted 22 December 2013 Available online 5 January 2014 Keywords: Conflict adaptation Dorsolateral PFC (DLPFC) Regional homogeneity (ReHo) Resting-state fMRI Conflict adaptation has been widely researched in normal and clinical populations. There are large individual dif- ferences in conflict adaptation, and it has been linked to the schizotypal trait. However, no study to date has ex- amined how individual differences in spontaneous brain activity are related to behavioral conflict adaptation (performance). Resting-state functional magnetic resonance imaging (RS-fMRI) is a promising tool to investigate this issue. The present study evaluated the regional homogeneity (ReHo) of RS-fMRI signals in order to explore the neural basis of individual differences in conflict adaptation across two independent samples comprising a total of 67 normal subjects. A partial correlation analysis was carried out to examine the relationship between ReHo and behavioral conflict adaptation, while controlling for reaction time, standard deviation and flanker in- terference effects. This analysis was conducted on 39 subjects' data (sample 1); the results showed significant positive correlations in the left dorsolateral prefrontal cortex (DLPFC) and left ventrolateral prefrontal cortex. We then conducted a test-validation procedure on the remaining 28 subjects' data (sample 2) to examine the re- liability of the results. Regions of interest were defined based on the correlation results. Regression analysis showed that variability in ReHo values in the DLPFC accounted for 48% of the individual differences in the conflict adaptation effect in sample 2. The present findings provide further support for the importance of the DLPFC in the conflict adaptation process. More importantly, we demonstrated that ReHo of RS-fMRI signals in the DLPFC can predict behavioral performance in conflict adaptation, which provides potential biomarkers for the early detec- tion of cognitive control deterioration. © 2014 Elsevier Inc. All rights reserved. Introduction It is important for people to control thoughts and behaviors. How- ever, individuals vary greatly in their control ability. For example, some people can control the impulse to smoke, whereas others cannot suppress their craving, despite being aware of the hazards of cigarettes. From the viewpoint of cognitive psychology, such variation represents individual differences in cognitive control. The main function of cognitive control is to accomplish goal-directed behaviors by moni- toring interference or response conflict, and dynamically adjusting performance (Botvinick et al., 2001; Egner, 2011). Such dynamic ad- justments can be studied via the “conflict adaptation effect” (Egner, 2007; Gratton et al., 1992; Tang et al., 2013), which is frequently observed in congruency tasks, such as the Eriksen flanker task (Eriksen and Eriksen, 1974). In the flanker task, participants are required to respond to target stimuli while ignoring flanking stimuli that may suggest the same response as the target (congruent trial, C) or an opposite response to the target (incongruent trial, I). Subjects typically respond more slowly to incongruent than to congruent trials, and the performance difference in terms of incongruent minus congruent trial reaction times (RTs) is a classic flanker interference effect. The conflict adaptation effect refers to the tendency in which the interference effect following an incongruent trial (II–IC) is smaller than that following a congruent trial (CI–CC) (Egner, 2007; Gratton et al., 1992; Tang et al., 2013). Task-based functional magnetic resonance imaging (fMRI) has been used to study the underlying neural basis of conflict adaptation. This has revealed strong links to the prefrontal cortex, especially the anterior cingulate cortex (ACC) and dorsolateral prefrontal cortex (DLPFC). The ACC appears to be associated with the function of conflict mon- itoring (Botvinick et al., 2001, 2004; MacDonald et al., 2000), while the DLPFC is involved in attempts to resolve conflict by transiently amplifying neural representations of task-relevant information and/or suppressing the processing of irrelevant information (Biswal et al., 1995; Egner and Hirsch, 2005a; Posner and Dehaene, 1994; Zhang et al., 2012). However, there are large individual differences in conflict adapta- tion. These differences have been used to explore specific cognitive NeuroImage 90 (2014) 146–152 ⁎ Corresponding author at: Faculty of Psychology, Southwest University, BeiBei District, Chongqing, China. E-mail address: xscat@swu.edu.cn (A. Chen). 1053-8119/$ – see front matter © 2014 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.neuroimage.2013.12.055 Contents lists available at ScienceDirect NeuroImage journal homepage: www.elsevier.com/locate/ynimg