Electronic Thesis and Dissertation Repository

Thesis Format

Integrated Article

Degree

Master of Science

Program

Neuroscience

Supervisor

Heath, Matthew

Abstract

The present work examined whether oculomotor deficits associated with a sport-related concussion (SRC) reflect an impairment to executive-based planning mechanisms or a task-based increase in concussion symptomology (e.g., headache, vertigo). Therefore, I employed a standardized measure of SRC symptom severity (SCAT-5), antisaccade performance and pupillometry metrics in persons with a SRC during early (i.e., initial assessment: ≤12 days post-SRC) and later (i.e., follow-up assessment: 14-30 days post-SRC) stages of recovery. In the initial assessment, the SRC group yielded longer reaction times (RT) (p=0.001), increased directional errors (p=0.002) and larger task-evoked pupil dilations (TEPD) (p=0.004) than the control group. The follow-up assessment indicated that RTs did not reliably vary between groups (p=0.155); however, the SRC group demonstrated more directional errors and larger TEPDs (p<0.03). Moreover, SCAT-5 symptom severity indicated that the oculomotor assessment did not increase symptom burden (p=0.622). Accordingly, I propose that a SRC impairs executive-based oculomotor planning mechanisms.

Summary for Lay Audience

Executive function is a component of cognition that supports our ability to process and respond to single and multiple stimuli, maintain task goals in working memory, and assert high-level inhibitory control. Indeed, executive dysfunction has been identified as a persistent issue in individuals who sustain a sport-related concussion (SRC). The antisaccade task (i.e., eye movement mirror-symmetrical to a target) may serve as an effective tool for the identification and management of executive dysfunction following a SRC. Convergent evidence indicates that persons with a SRC exhibit longer antisaccade reaction times and produce more directional errors than their age-matched healthy controls during their concussion recover – deficits that persist even when the clinical signs of a SRC resolve. It is, however, unclear whether antisaccade performance deficits directly relate to impaired executive control or reflect a task-based increase in symptom burden (e.g., difficulty concentrating, headache, vertigo) associated with the administration of the antisaccade task. Therefore, the current study employed a standardized SRC concussion symptom checklist (i.e., Sport Concussion Assessment Tool: SCAT-5) in combination with antisaccade performance and pupillometry measures in persons with a SRC – and their age- and sex-matched controls – during the early (≤12 days post-SRC) (i.e. initial assessment) and later (14-30 days post-SRC) (i.e. follow-up assessment) stages of recovery. I included a measure of pupil dilation during antisaccade planning because some work has suggested that increased pupil dilation provides a proxy for increased executive demands in response preparation. At the initial assessment, the SRC group exhibited longer antisaccade reaction times, increased directional errors and larger pupil dilations than the control group. At the follow-up assessment, the SRC and control groups demonstrated comparable reaction times; however, the former continued to demonstrate increased directional errors and larger pupil dilations. SCAT-5 symptom scores indicated that the oculomotor assessment did not influence task-based symptom burden. The results therefore demonstrate that antisaccade performance deficits following a SRC relate to executive dysfunction in the planning mechanisms supporting antisaccades, and further suggest that the antisaccade task may serve to support SRC diagnosis and management.

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