Working memory recovery in adolescents with concussion: Longitudinal fMRI study

Abstract

Background: Understanding behavioral and neural underpinnings of post-concussion recovery of working memory function is critically important for improving clinical outcomes and adequately planning return-to-activity decisions. Previous studies provided inconsistent results due to small sample sizes and the use of a mixed population of participants who were at different post-injury time points. Methods: To better understand behavioral and neural correlates of working memory recover during the first 6 months post-concussion, we used functional magnetic resonance imaging (fMRI) to scan 45 concussed adolescents [CONC] at baseline (<10 days post-concussion) and again at 6 months post-concussion. Healthy control [HC] adolescents without a history of concussion were scanned once. During the scans, participants performed 1-back (easy) and 2-back (difficult) working memory tasks with the letters as the stimuli and angry, happy, neutral, and sad faces as distractors. Results: By the 6-month follow-up, all affected adolescents were asymptomatic and cleared to return-to-activity. Working memory function recovery was reflected by faster and more accurate performance at 6 months vs. baseline (p-values<0.05). It was also characterized by significant difficulty-related activation increases in the left inferior frontal gyrus (LIFG) and the left orbitofrontal cortex (LOFC) at 6 months vs. baseline. Conclusion: Post-concussion recovery is associated with significant performance improvements in speed and accuracy, as well as normalization of brain responses in the LIFG and LOFC during the n-back task. The observed patterns of LOFC activation might reflect compensatory strategies to distribute neural processing and reduce neural fatigue post-concussion.