Author ORCID Identifier

https://orcid.org/0000-0002-9905-9736

Year of Publication

2021

Degree Name

Doctor of Philosophy (PhD)

Document Type

Doctoral Dissertation

College

Health Sciences

Department

Rehabilitation Sciences

First Advisor

Dr. Matthew C. Hoch

Abstract

The ability to mitigate performance decrements during the concurrent completion of cognitive and motor tasks (i.e., dual task (DT)) deteriorates in patients with mild Traumatic Brain Injury (mTBI). It is theorized that the long-term sequelae of mTBI are due to the return to full activity prior to neurophysiologic healing. To mitigate the negative outcomes associated with mTBIs, translational clinical research of neurophysiologic recovery is of paramount importance for both athletic and non-athletic populations. Despite the well-known health consequences, clinical decisions regarding neurophysiologic recovery and return to activity remain problematic for clinicians. Return to activity decisions are currently based on normalization of cognitive tests, observer scored static balance measures, and resolution of self-reported symptoms. Postural control tests used for clinical decision making are able to detect acute deficits in mTBI. However, the utility of these measures has come into question as they either lack objective measures of static postural control, are too expensive for widespread clinical adoption, experience ceiling effects, and/or fail to replicate the task demands of sport and daily environmental interactions. DT gait has emerged as a sensitive method for identifying persistent motor deficits in mTBI. The capacitance sharing model states that during simple DTs there are ample neural resources available to optimize and maintain motor and cognitive performance. Cognitive tasks completed during difficult postural conditions, requiring higher levels of neuronal activation, would therefore create competition between cognitive and motor systems. However, the subsequent cognitive-motor interference patterns are not well understood. Determining the influence of sensory modality perturbations, delivered through clinical balance and gait test, on cognitive-motor interactions has the potential to clarify principles of the capacitance sharing model for clinical integration into mTBI. Moreover, there is a dearth of evidence regarding how nervous system networks change in response to mTBI and how the functionality of these networks influences one’s ability to conserve gait and balance performance across DT conditions. Therefore, the purpose of this dissertation was to 1) determine the directionality and network specificity of connectivity changes due to mTBI through a systematic review of the extant literature 2) determine how cognitive-motor interactions change across task demands and 3) to determine neurophysiologic mechanisms underlying DT performance in healthy, young adults. The findings of this dissertation provide additional insight into DT control theories, such as the capacitance sharing model, cognitive-motor interactions appear to be task specific. Moreover, these results demonstrate that cortical networks which demonstrate altered function post-mTBI are associated with the capacity to flexibly accommodate to DT gait and postural control conditions. These findings serve as a fundamental framework for future extension into understanding neurophysiologic recovery and DT deficits in mTBI.

Digital Object Identifier (DOI)

https://doi.org/10.13023/etd.2021.044

Available for download on Sunday, April 23, 2023

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