4.7 Preserved Inhibitory Function in Healthy Children During a Stroop Test: an fNIRS Study

Abstract

Functional near-infrared spectroscopy (fNIRS) is a noninvasive, relatively motion-tolerant method for measuring hemodynamic changes, reflecting neural activity. Although it has an advantage in children, the clinical utility of fNIRS is partly limited by the lack of normative data. Therefore, in this study, we measured fNIRS signals while performing cognitive tasks in healthy children. A total of 22 children aged 8-15 years who had no past psychiatric history were enrolled. After exclusion of multichannel rejected data, 8 boys and 12 girls (11.9 ± 2.1 years of age) were analyzed. The STROOP Color and Word Test was composed of 3 different stimuli lasting 45 seconds [word phase, W; color phase, C; and color-word phase, CW], with a 30-second resting phase between stimuli. We used NIRSIT LITE for kids (OBELAB, Korea), which is a 15-channel neuroimaging system for the prefrontal cortex. Data analyses were conducted using NIRSIT Analysis Tool version 3.1. and IBM SPSS Statistics software, version 25.0. Through a time-series graph, it was confirmed that oxyhemoglobin (HBO) increased and deoxyhemoglobin (HBR) decreased in the frontal lobe during the Stroop task. When comparing within the test, the degree of HBO increment was W>C>CW. When the general linear model analysis was performed, statistically significant differences were found in the right orbitofrontal cortex and frontopolar prefrontal cortex (channel 7) in W (t = 3.85; p = 0.002) and C (t = 4.29; p = 0.001) while comparing with the resting phase. Although inconsistent stimuli (CW) require more complex prefrontal function (inhibit cognitive interference, cognitive flexibility, and working memory) than neutral stimuli (W) or concordant stimuli (C), no area showed a difference in activity compared to that in the resting state in CW. This result shows that in the healthy group, the processing of interference stimuli works well without much cognitive effort. Among the Stroop tasks in healthy children, the word phase was found to activate the frontal lobe the most. In our study, it was confirmed that the inhibitory function required for the Stroop task works well in typically developing children, and it can be functionally measured using fNIRS. In the future, a comparison between healthy children and a group of children with neurodevelopmental disorders such as ADHD will be necessary.