Impairments in processing speed under conditions of increasing cognitive load have been reported in individuals with mild traumatic brain injury (mTBI). In other conditions that are also associated with white matter disruption, both psychological distress and fatigue have been shown to underlie this impairment.

Objective: the current study aimed to investigate whether slowing of processing abilities under conditions of greater cognitive load is independent of fatigue and psychological status in premorbidly healthy individuals with subacute mTBI.

Method: using a prospective observational design, we examined 84 individuals with mTBI approximately 8 weeks after injury and 47 healthy control (HC) participants. They were assessed with the Symbol Digit Modality Test, an n-back task and a rate of gain of information choice reaction time task that conforms to Hick’s law. Participants were also assessed with measures of fatigue and psychological status.

Results: as expected, findings revealed no group differences on simple reaction time tasks, but as task complexity increased, the mTBI group performed more slowly than the HC group. This group difference occurred independently of fatigue and psychological distress levels and was associated with a moderate effect size.

Conclusions: during the subacute period after mTBI, premorbidly healthy individuals demonstrate impairment in their ability to rapidly process information as the cognitive load of the task increases beyond simple reaction time requirements. Examination of whether these changes affect resumption of premorbid roles is warranted.

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2021
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