dc.description.abstract | Inhibitory control has a significant improvement in preschool period. Conflict monitoring and motor response inhibition both are types of inhibitory control, and children with frontal lobe dysfunctions, such as attention-deficit hyperactivity children (ADHD), show deficits in these two types of inhibitory control. Many developmental studies have indicated that the prefrontal lobe cortex, which is a region that plays an important role in the inhibitory control, continues mature in preschool stage. However, few studies have integrated the neural correlates of inhibitory control with the development of conflict monitoring and motor response inhibition in typically developing preschool children.
In this thesis, a child version of the flanker task and the stop signal task were used to investigate the behavioral performance and the corresponding event-related potentials (ERPs) of conflict monitoring and motor response inhibition in 5 and 6 years of age. In Experiment 1, we assessed whether congruency effect and the N2 effect were detectable when preschool children performed the child version of the flanker task. Our results showed that the congruency effect and N2 effect (350 - 500 ms) were observed in 5- and 6-years-old children, but did not improve with age between 5 and 6 years. In Experiment 2, we measured the stop signal reaction time (SSRT) and the N2 effect in the stop signal task with 5 and 6 years old preschoolers. The behavioral results indicated that the response inhibition significantly improved with age in 5 and 6 years old. However, we did not observe significant N2 (250 - 450 ms) difference between the successful inhibition condition and the failed inhibition condition in our preschoolers. Instead, we observed that a late positive wave (500 - 900 ms) was more positive-going in the failed inhibition than in the successful inhibition. Late positive component in preschoolers can be associated with the processing of an error event that has been referred to as “error positivity” or Pe. These results suggest that the processes of the inhibitory control indexed by the N2 component have not yet been well-developed when 5 and 6 years old preschoolers performed the stop signal task. On the other hand, it seems that the preschoolers are in the processing of developing the cognitive capability in error detection and correction, as reflected by the late positive component.
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