Date of Award
Doctor of Philosophy
Brain injuries are one of the leading causes of disability and death globally, and prevalence numbers indicate an increase of injuries each year. Brain injuries significantly burden the individual afflicted; the effects of brain injuries are felt across families and relationships, and society at large. Brain injuries are often complicated by co-morbid socially significant health disorders, from mental health to financial and challenging behavior (i.e., aggression). The presence of these can severely limit access to community and rehabilitative opportunities. Some common characteristics underlying these socially significant problems are executive dysfunction and impulsivity. The literature broadly points to the role of executive functioning in impulsivity, indicating that when these processes are inadequate, impulsivity is more severe. To complicate, impulsivity research within brain injury is not broad. Additionally, little consensus exists on the concept and how stable this behavior is, and whether impulsivity can be improved. An area of impulsivity research, delay discounting, has gained increased attention from behavior scientists in the past 30 years because of its pragmatic approach to impulsivity. Delay discounting is a trans-disease process and various clinical populations discount delayed rewards at a high rate. The few studies that exist indicate that brain-injured people also discount at a higher rate compared to controls. Furthermore, high delay discounting have well-established connections with other socially significant health disorders. Due to the lack of breadth of the discounting literature in brain injury research, one exciting area is temporal stability and clinical interventions to decrease discounting. In a set of two studies, the aim was to expand the current knowledge on temporal stability, connections to socially significant behavior and deficits, and the effects on clinical interventions to reduce discounting. Study 1 examined the relationship between responses on discounting tasks at two different times and the relationship between discounting and measures of challenging behavior and executive functions. This study indicates that discounting was stable, that challenging behavior is related to higher rates of discounting yet did not find a relationship with executive functioning. Study 2 investigated the effects of computerized cognitive training and mindfulness training on discounting, executive functioning, and challenging behavior in multiple baseline research design across three participants. Results indicated that a small and transient improvement in delay discounting was observed for two of three participants during the computerized cognitive training. The improvement increased once the mindfulness training was introduced for the same two participants. Improvements were observed on executive functioning measures for all participants, and limited improvements were observed from measures of challenging behavior. Together these findings add to the body of literature on delay discounting and brain injury by demonstrating temporal stability and to the literature on clinical interventions to reduce high rates of delay discounting
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