Brain activation during working memory 1 month after mild traumatic brain injury

TLDR

Many individuals report memory difficulties after MTBI, yet objective memory performance can remain normal. The study aimed to assess patterns of regional brain activation in response to varying working memory loads shortly after mild traumatic brain injury. Brain activation patterns during an auditory n‑back task were measured with functional MRI in 12 MTBI patients within one month of injury and 11 healthy controls. MTBI patients exhibited increased activation in right parietal and right dorsolateral frontal regions during high load compared to controls, while task performance was similar, suggesting altered working memory circuitry despite preserved performance.

Abstract

<b><i>Objective:</i></b> To assess patterns of regional brain activation in response to varying working memory loads shortly after mild traumatic brain injury (MTBI). <b><i>Background:</i></b> Many individuals complain of memory difficulty shortly after MTBI. Memory performance in these individuals can be normal despite these complaints. <b><i>Methods:</i></b> Brain activation patterns in response to a working memory task (auditory n-back) were assessed with functional MRI in 12 MTBI patients within 1 month of their injury and in 11 healthy control subjects. <b><i>Results:</i></b> Brain activation patterns differed between MTBI patients and control subjects in response to increasing working memory processing loads. Maximum intensity projections of statistical parametric maps in control subjects showed bifrontal and biparietal activation in response to a low processing load, with little additional increase in activation associated with the high load task. MTBI patients showed some activation during the low processing load task but significantly increased activation during the high load condition, particularly in the right parietal and right dorsolateral frontal regions. Task performance did not differ significantly between groups. <b><i>Conclusion:</i></b> MTBI patients differed from control subjects in activation pattern of working memory circuitry in response to different processing loads, despite similar task performance. This suggests that injury-related changes in ability to activate or to modulate working memory processing resources may underlie some of the memory complaints after MTBI.