Date of Award

Spring 2023

Project Type


Program or Major

Communication Sciences and Disorders

Degree Name

Master of Science

First Advisor

Donald A Robin

Second Advisor

Amy E Ramage

Third Advisor

Joanna Gyory


ABSTRACTMOMENT-TO-MOMENT FLUCTUATIONS IN SUSTAINED ATTENTION IN INDIVIDUALS WITH TRAUMATIC BRAIN INJURY By Kelly Marinick University of New Hampshire Introduction: The present study examined moment-to-moment variations in reaction time (RT) using the Complexity Estimate (CE), a measure of system entropy. The primary hypothesis explored whether system entropy (CE) is higher in mild TBI (TBI) compared to neurologically healthy controls. The secondary hypothesis was to examine whether system entropy increases with task difficulty in both populations, but to a greater extent in those who have experienced TBI. Methods: 27 individuals who had experienced a TBI and 22 neurologically healthy individuals aged between 18-35 years were recruited to the Cognition, Brain, and Language Team (CoBALT) lab at the University of New Hampshire Department of Communication Sciences and Disorders research laboratories. The Starry Night task was employed to measure sustained attention in individuals with TBI and the control group, in order to investigate whether processing speed in individuals with TBI is more variable than neurologically healthy individuals. This study is a retrospective analysis of a repeated measures design that uses a mixed model to explore the effect of Group (TBI versus control), Task Complexity, and their interaction on the response variable of the Complexity Estimate, which is an index of reaction time (RT) variability. Results: Task Complexity and Group were both significant predictors of RT Complexity. There was a significant interaction between Task Complexity and Group (F Ratio = 4.28, p-value = 0.0167), indicating that the effect of Group on RT Complexity depends on the level of the Task Complexity. This implies that reaction time complexity is influenced by both the participant’s group and the complexity of the task they are performing. It was observed that there was no difference in RT complexity for the control group, however in the TBI group, there was a difference in reaction time based on the task’s complexity. The variance component of the random effect (Study Subject) was 0.118 (CI: 0.002 to 0.235, Wald p-value=0.0469), indicating that there is significant variability in RT Complexity among individuals in response to Task Complexity and Group. Discussion: The study results suggest that system entropy is higher in individuals with TBI compared to neurologically healthy individuals. Additionally, as task difficulty increases, system entropy increases in both populations, with a greater increase observed in individuals with TBI. Measures of RT complexity proved to be a valuable indicator of increased system entropy resulting from task difficulty. Together these findings offer insight into how individuals with TBI prioritize and allocate their attention in complex environments, which can assist in developing interventions that address attentional deficits in individuals with TBI.