Alterations in Sensorimotor Function in Populations At Risk for Neurodegenerative Disorders

Abstract

It is well-established that concussion, a form of mild traumatic brain injury (mTBI), is a diffuse injury to the brain, producing a broad range of impairments. Such impairments include impaired sensorimotor integration, or the capability of the central nervous system to integrate different sources of stimuli and transform them into motor actions. Strong evidence for brain-related pathologies and increasing reports of long-term symptoms following COVID-19 infection, regardless of severity or presentation of symptoms, resembles that of mTBI. Additionally, producing no clinically observable symptoms of mTBI, sub-concussive loading increases the risk of neurological injury and degeneration, with neurophysiological impairments identified in individuals who displayed no clinically observable signs or symptoms of mTBI. With exposure to repetitive sub-concussive loading (RSCL), as seen in contact-sport and military settings, these impairments may accumulate to mTBI-like impairment. The use of sensorimotor integration techniques, including postural control, oculomotor control and cortical activation may detect even mild alterations in sensorimotor function without clinically observable symptoms. In this dissertation we sought to expand our understanding of the disease and injury states in which sensorimotor function is altered by examining function in two distinct samples: individuals with a history of COVID-19 infection and an RSCL exposure group. Our overarching hypotheses were that (i) markers of altered sensorimotor function would be evident during postural control performance in individuals with a history of COVID-19 infection, (ii) markers of altered sensorimotor function would be evident during oculomotor control performance in individuals with a history of COVID-19 infection, and (iii) markers of altered sensorimotor function would be evident during oculomotor control performance and in accompanying cortical activation measures following exposure to a single bout of RSCL through soccer heading. Our findings provide partial support for our hypotheses. No statistically significant markers of altered sensorimotor function were identified during postural control performance in the COVID-19 sample, but markers of altered sensorimotor function were seen during oculomotor control performance in both the COVID-19 and RSCL exposure samples. We identified altered gaze behavior during horizontal smooth pursuit performance across both COVID-19 and RSCL exposure samples, with lower gaze complexity orthogonal to the target trajectory during linear task performance present in the COVID-19 groups and following the RSCL exposure period as compared to the CONTROL and PRE-exposure measurements. Additional changes in gaze behavior during HSP performance and non-significant increases in cortical activity were also present in the RSCL exposure sample following the exposure period.