Oculomotor Cognitive Control Abnormalities in Australian Rules Football Players with a History of Concussion

Abstract

This study used oculomotor, cognitive, and multi-modal magnetic resonance imaging (MRI) measures to assess for neurological abnormalities in current asymptomatic amateur Australian rules footballers (i.e., Australia's most participated collision sport) with a history of sports-related concussion (SRC). Participants were 15 male amateur Australian rules football players with a history of SRC greater than 6 months previously, and 15 sex-, age-, and education-matched athlete control subjects that had no history of neurotrauma or participation in collision sports. Participants completed a clinical interview, neuropsychological measures, and oculomotor measures of cognitive control. MRI investigation involved structural imaging, as well as diffusion tensor imaging and resting-state functional MRI sequences. Despite no group differences on conventional neuropsychological tests and multi-modal MRI measures, Australian rules football players with a history of SRC performed significantly worse on an oculomotor switch task: a measure of cognitive control that interleaves the response of looking towards a target (i.e., a prosaccade) with the response of looking away from a target (i.e., an antisaccade). Specifically, Australian footballers performed significantly shorter latency prosaccades and found changing from an antisaccade trial to a prosaccade trial (switch cost) significantly more difficult than control subjects. Poorer switch cost was related to poorer performance on a number of neuropsychological measures of inhibitory control. Further, when comparing performance on the cognitively more demanding switch task with performance on simpler, antisaccade/prosaccades tasks which require a single response, Australian footballers demonstrated a susceptibility to increased cognitive load, compared to the control group who were unaffected. These initial results suggest that current asymptomatic amateur Australian rules football players with a history of SRC may have persisting, subtle, cognitive changes, which are demonstrable on oculomotor cognitive measures. Future studies are required in order to further elucidate the full nature and clinical relevance of these findings.

Diffusion MRI abnormalities in adolescent rats given repeated mild traumatic brain injury

“…It should also be noted that our MRI study was conducted on ex vivo brain samples, which somewhat limits the clinical relevance of the findings. However, both the scan time (i.e., 2 h) and the DWI sequences that were used are appropriate for future in vivo studies 23, 31, 57. As our current study only investigated rats given repeated mTBI, future in vivo studies could investigate the effects of a single mTBI using serial MRI at different postinjury times.…”

“…However, both the scan time (i.e., 2 h) and the DWI sequences that were used are appropriate for future in vivo studies. 23,31,57 As our current study only investigated rats given repeated mTBI, future in vivo studies could investigate the effects of a single mTBI using serial MRI at different postinjury times. Such investigations would provide important information related to diagnosis and recovery/cerebral vulnerability after a single mTBI.…”

Clinical validation of an optimized multimodal neurocognitive assessment of chronic mild TBI

“…As expected, 15 the more‐challenging 1‐Back subtest provided superior classification of chronic mTBI relative to the 0‐Back subtest. Considering similar findings with other eye movement tasks, 28‐30 it appears likely that the additional working memory demands were instrumental in illuminating impairment related to chronic mTBI.…”

“…Impaired eye movements have been linked to axonal injury in postmortem tissue and on diffusion tensor imaging; 23‐25 abnormal functional connectivity in chronic mTBI extends to the visual system and its interactions with higher‐order cognitive processing 26 . Importantly, the types of eye movements that are most strongly impacted by mTBI are those that most heavily rely upon effective cognitive processing, as opposed to measures of basic neuromotor function 14,18,27‐29 . In particular, previous research conducted by our group 14,15 and others 28‐30 has shown enhanced sensitivity of eye movements to effects of mTBI under conditions of increased cognitive load.…”

“…Importantly, the types of eye movements that are most strongly impacted by mTBI are those that most heavily rely upon effective cognitive processing, as opposed to measures of basic neuromotor function 14,18,27‐29 . In particular, previous research conducted by our group 14,15 and others 28‐30 has shown enhanced sensitivity of eye movements to effects of mTBI under conditions of increased cognitive load. Many oculomotor metrics are also less impacted by age, education, or intelligence, relative to conventional neuropsychological measures 20,31,32 …”