Impaired practice effects following mild traumatic brain injury

Background: The negative effects of mild traumatic brain injury (mTBI) on attention are well established. Effects of practice on neuropsychological test performance have also been long recognized and more recently linked to electrophysiological indices of information processing. Objective: The current study examined the behavioural and electrophysiological impact of mTBI on consistent practice of a neuropsychological test of attention. Research design: Prospective cohort study. Methods: Adult participants with a history of mild TBI (n=10; time since injury > 2 months, mean=15.2 months) and healthy matched controls (n=10) completed the Paced Auditory Serial Addition Task (PASAT) at four separate sessions. Event-related potentials (ERPs) were simultaneously recorded. Results: Accuracy of PASAT performance in both groups improved significantly with practice. In healthy controls behavioural improvements were associated with significant attenuation of a frontally distributed ERP component marker of executive attention. These executive attention demands did not appear to ease with consistent practice in the mTBI group, who also endorsed more concussion-related symptoms. Conclusions: These preliminary results suggest sustained mental effort is required to achieve 'normal' performance levels following mTBI and support the use of practice-related, ERP indices of recovery from mTBI as a sensitive correlate of persistent post-concussion symptoms.