Resting brain connectivity deficits in service members with mTBI and PTSD associated with working memory performance
By Conor Gormally. This article was initially published in our Concussion Update newsletter; please consider subscribing.
A study by Adam Runyan et al. found that active duty service members with a history of mild traumatic brain injury (mTBI) with persisting cognitive symptoms and service members with PTSD had similarly lower levels of resting state functional connectivity (rsFC) in regions associated with working memory compared to service members with an orthopedic injury. rsFC represents the degree of communication between different regions of the brain. Runyan et al. believe that “the neural mechanisms contributing to cognitive symptoms in mTBI and PTSD may be similar. If this were the case, co-morbid mTBI and PTSD may contribute to further hypoconnectivity [lower connectivity] of these working memory regions and more significant working memory deficits,” pointing to the potential for an additive effect. The study was published in Brain Research.
Was lower rsFC associated with working memory performance in these individuals? Yes, the authors found a strong correlation between lower rsFC in the ventrolateral prefrontal cortex (involved in emotion, reward, motivation, threat detection, and fear in addition to working memory) and working memory performance in participants. The authors discuss several potential treatments for these issues. While “cognitive training interventions can improve working memory and reduce symptoms in mTBI and PTSD,” other studies have indicated that these improvements may be only for the specific training task and not generalizable to broader working memory problems. The authors also discuss research on neurostimulation via transcranial magnetic stimulation or transcranial direct current stimulation.
While rsFC deficits in mTBI and PTSD were generally similar, individuals with PTSD had worse rsFC in some working memory regions, as well as regions associated with the sensorimotor system (response inhibition and integration of sensory information) and with the dorsal attention network (orienting focus to a particular task or object). This study is the first to “directly compare rsFC of working memory network regions in individuals with mTBI versus PTSD,” though the population is relatively specific; participants were majority white, vast-majority male, and groups had an average age between 32 and 37.