Date of Award
Doctor of Philosophy
Inhibitory control, described as the ability to suppress one response in favor of a goal-directed response, is thought to play an important role in the development of emotional regulation as well as various forms of psychopathology, including ADHD. Up until very recently, inhibitory control has been researched within two completely separate fields of study: temperament and neuropsychology. In the temperament/personality literature, inhibitory control is a major component of the overarching temperament/personality factor of Effortful Control/Conscientiousness. In the field of neuropsychology, inhibitory control is considered one aspect of executive function. Further complicating the current understanding of inhibitory control is the complexity of the underlying neural networks implicated in inhibitory control. This study examined inhibitory control in temperament and executive function in children with and without ADHD, and it explored the relationship between inhibitory control and the superior frontal cortex (SFC) and orbital frontal cortex (OFC) volumes. In order to assess subareas of the OFC and SFC, an innovative parcellation method was used. Results suggested that the temperament and executive function measures of inhibitory control did form a single factor as long as they were measured within the same modality, parent-report. In contrast, the performance-based measure of inhibitory control was not correlated with any of the parent-report measures of inhibitory control and was, therefore, analyzed separately in relation to OFC and SFC volumes. Parent-rated inhibitory control was predicted by ADHD status only, but exploratory analyses suggested that left anterior SFC, right and left anterior medial OFC, and gender were related to parent-rated inhibitory control. In contrast, performance-based inhibitory control was predicted by gender and left SFC, specifically posterior left SFC. Taken together, these findings suggest a conceptual overlap between temperament and executive function that brings together two areas of the literature and has implications for the understanding of various forms of psychopathology characterized by deficits in inhibitory control. This study provides evidence for the role of the SFC and the OFC in inhibitory control, depending upon the measurement method, and contributes to the broader understanding of the neural mechanisms of inhibitory control in children.
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