Date of Award

Spring 2022

Document Type

Open Access Dissertation

Department

Exercise Science

First Advisor

Troy Herter

Second Advisor

Robert Davis Moore

Abstract

Each ach year a growing number of individuals report lingering deficits months-years following concussion. Persistent post-concussion symptoms (PPCS) can negatively impact day-today activities and if left untreated may manifest in severe neurological sequelae resulting in long-term cognitive impairment or advanced neurological degeneration (i.e., CTE). Current clinical diagnostic and prognostic assessments (e.g., symptom reports and neurocognitive testing) lack the sensitivity to quantify neurological function. Accordingly, there is a critical need to identify objective biomarkers specific to PPCS to improve an individual’s quality of life and prevent severe long-term neurological dysfunction.

Psychophysiological measurements (e.g., EEG derived event-related potentials, heart rate variability, and indices of pupil dynamics) utilize involuntary fluctuations in organ behavior (brain potentials, heart rate, pupil size) in response to environmental events quantify higher-order neurological function. Numerous studies have indicated significant alterations in psychophysiological function in both acute (days-weeks) and chronic (months-years) phases of concussion recovery. These studies demonstrate that psychophysiological measures may possess the necessary sensitivity to serve as reliablemeasures of concussion recovery. However, previous methodological limitations have restricted cross study comparisons and implementation into clinical settings. Specifically, few research studies directly compare currently asymptomatic and symptomatic individuals with a recent history of concussion. This comparison is critical as previous research has demonstrated neurological deficits months to years following injury. By excluding this comparison analytical interpretations fail to account for neurological adaptations that may underlie typical recovery patterns. Additionally, traditional psychophysiological assessments employ task paradigms that do not fully capture the complexity of real-world engagement. If a task is too simplistic, it may fail to adequately challenge the individual and may not reveal lingering neurological dysfunction when completing tasks in the real-world.

The present series of investigations found demonstrated that symptomatic individuals with a history of concussion report significant symptom burden spanning somatic disruptions, psycho-affective health, and general quality of life. Furthermore, symptomatic individuals demonstrated significant deficits in tasks of cognitive control, executive function, and attention. These deficits were exacerbated by more complex tasks designed to mimic real-world interactions. In addition to behavioral deficits, both symptomatic and asymptomatic individuals tended to demonstrate lingering deficits in psychophysiological function (i.e., pupillometry and ERPs). Unfortunately, ERP measures collected during more dynamic and complex tasks produced muted waveforms making comparisons across groups difficult. Finally, deficits in both cognitive performance and psychophysiological behavior demonstrated significant relationships with reported symptom burden. This supports their use as potential biomarkers of neurological dysfunction following concussion. In conclusion, the present series of studies supports the growing body of literature suggesting slow-to-recovery demonstrate lingering impairments in neurological function. Furthermore, behavioral assessments designed to mimic real-world interactions may more precisely capture day-to-day impairments. However, these tasks may be too complex and therefore distort neuroelectric recordings of cognitive function

Rights

© 2022, Adam Todd Harrison

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