Investigating the Relationship Between MHI, Cognitive Fatigue, and EDA
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Mild head injury (MHI) has been associated with various debilitating effects leading to impairments in many individuals which can be long-lasting. Some of the effects can be explained by disruption to the brain as a result of acceleration, deceleration and rotational forces which lead to axonal stretching and tearing. The ventromedial prefrontal cortex (VMPFC) is particularly vulnerable following MHI and has been associated with attenuated autonomic arousal as indicated by electrodermal activity (EDA). These neural disruptions and its associated physiological underarousal may explain some of the consequences of MHI. Cognitive fatigue is a known consequence of MHI and is defined as an increase in mental exhaustion due to prolonged mental effort and a lack of cognitive resources to sustain mental activity and performance. Increases in autonomic physiological arousal have been found to contribute to sustained performance and attention, but eventually can lead to cognitive fatigue. As such, those who have sustained a MHI and live with attenuated arousal may be disadvantaged when engaging in cognitive tasks. This study investigates the effects of cognitive fatigue, EDA, and task performance following MHI in university students. Forty-two university students (38% MHI) completed self-report questionnaires on general, and cognitive, fatigue and completed a series of simple, but increasingly demanding, cognitive tasks. Physiological arousal was measured by EDA throughout. Individuals with MHI reported significantly greater levels of cognitive fatigue relative to their no-MHI cohort at baseline. Interestingly, participants with MHI also reported greater capacity for recovery from cognitive fatigue which may imply an inability to self-monitor. Even so, while both groups demonstrated initial heightened EDA activation that significantly declines over the course of completing the cognitive tasks, there were no observable performance differences between the groups in terms of accuracy (which declined across tasks), response time (which increased across tasks), or self-reported cognitive fatigue at completion of testing. Future research will focus on establishing improved measures for assessing acute cognitive fatigue across tasks, as well as challenging cognitive tasks that induce measurable cognitive effort independent of cognitive capability.