Abstract
Conflict processing is crucial for humans and has been investigated using hemodynamic and electrophysiological measures. However, because most previous research has studied hemodynamic and electrophysiological measures separately, the relationship between these two measures in conflict processing is poorly understood. In our study, we measure near-infrared spectroscopy (NIRS) and event-related potential (ERP) signals simultaneously in a Chinese color-word matching Stroop task and examine the relationship between the conflict-related hemodynamic signal in the prefrontal cortex (PFC) and electrophysiological signal. The results show significant Stroop effects for behavioral, NIRS (oxy-hemoglobin: HbO 2 ), and ERP [N450, late positive complex (LPC)] data. The significant N450 Stroop effect occurs before the behavioral response to incongruent stimuli, while the evident LPC Stroop effect occurs after it, suggesting that only N450 is associated with conflict processing. Additionally, N450 Stroop effects during the early and later phases are negatively correlated with HbO 2 Stroop effects in the left PFC and in the bilateral PFC, respectively. These results suggest that N450 reflects conflict detection and resolution, the left PFC may be involved in conflict detection, and the bilateral PFC is engaged in conflict resolution. Overall, the analysis of the correlation between hemodynamic and electrophysiological signals is useful for studying human brain function.
Highlights
Cognitive control is a key characteristic of the human cognitive system
We aimed to examine the relationship between the conflict-related hemodynamic signal and the electrophysiological signal by combining near-infrared spectroscopy (NIRS) and event-related potential (ERP)
We examined the relationship between the conflictrelated hemodynamic signal in the prefrontal cortex (PFC) and the electrophysiological signal during a Chinese color-word matching Stroop task
Summary
Cognitive control is a key characteristic of the human cognitive system. It refers to the ability to attend to goal-relevant information, ignore distracting information, overcome conflict, and select the appropriate response. Cognitive control over conflict usually relies on conflict detection and resolution, and it has been widely studied using the Stroop task. In the classic Stroop task,[1] subjects are instructed to identify the color in which a word stimulus is printed. Behavioral responses to incongruent stimuli (when the word and the ink color are incongruent, e.g., the word “blue” shown in green ink) are slower and less accurate than responses to neutral or congruent stimuli (when the word and the ink color are the same). The behavioral difference between incongruent and neutral or congruent stimuli is called the Stroop effect, which has been used as an index of cognitive control. Because the Stroop task is useful for studying neurological/psychiatric disorders,[2,3] investigating its neural correlates can both improve our
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