Decreased working memory capacity in the chronic phase of mild traumatic brain injury

Despite increasing recognition of the significance of mild traumatic brain injury (mTBI), our knowledge of the long-term cognitive impacts of the injury remains incomplete. Currently, the chronic mTBI literature conveys conflicting findings, likely in large part due to the use of measures that lack sensitivity to detect subtle cognitive changes and failures to consider individual differences in cognitive outcomes post mTBI. In addition, while it is well documented that a significant number of injuries go unreported, studies investigating individuals with a history of mTBI that capture these unreported injuries are lacking in comparison to those using hospital-based samples. In this preregistered study, we used a range of complex behavioural tasks to investigate cognitive performance in a large sample of individuals with self-reported history of mTBI (n=82) and a control group (n=88). We also explored whether individual differences in injury-related factors predict cognitive performance in the mTBI group. The findings revealed poorer verbal working memory performance in mTBI participants compared to controls. No group differences were observed on tasks assessing visual working memory, multitasking ability, cognitive flexibility, attentional control, visuospatial ability, or information processing speed. Furthermore, the individual differences analyses suggest that age at injury may be an important predictor of working memory performance in both verbal and visual domains following mTBI. Together, these findings indicate that mTBI may have lasting impacts on verbal working memory capacity and that injury-related factors, such as age when the injury occurred, may be crucial to consider when assessing cognitive outcome in individuals with a history of mTBI.