Arithmetic difficulties in children with mild traumatic brain injury at the subacute stage of recovery.AIM
 Arithmetic difficulties have been reported in children with mild traumatic brain injury (mTBI), but the electrophysiological abnormalities underlying these impairments remain unknown.  We therefore used event-related potentials (ERPs) to investigate brain functioning during arithmetic in children in the subacute phase after mTBI.


 The participants comprised 16 children with mTBI at the subacute phase of recovery (10 males, mean age 10y 8mo; six females, mean age 10y 8mo) and 16 well-matched comparison children (11 males, mean age 10y 11mo; five females, mean age 10y 6mo).  All children were asked to solve single-digit addition problems of small (sum ≤10) and large problem size (sum >10) and ERPs were simultaneously recorded.


 Children with mTBI performed significantly less accurately (mean 81%) than comparison children (mean 91%) on the large (p=0.026) but not on the small problems (p=0.171).  We observed no group differences in the early ERP components P1, N1, P2, and N2 (all p values ≥0.241), yet significant group differences (p=0.019) emerged for the late positivity component (LPC), which showed smaller mean amplitudes (mean 8.35μV) in mTBI patients than comparison children (mean 12.95μV).


 Immediately after the injury, arithmetic difficulties in children with mTBI are particularly pronounced on more complex arithmetical problems that are less automated.  This is reflected in the ERP pattern, with decreased LPC but normal N2 and early ERP components.
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