White matter integrity of the medial forebrain bundle and attention and working memory deficits following traumatic brain injury

Abstract

Abstract Background and Objective The medial forebrain bundle ( MFB ) contains ascending catecholamine fibers that project to the prefrontal cortex ( PFC ). Damage to these fibers following traumatic brain injury ( TBI ) may alter extracellular catecholamine levels in the PFC and impede attention and working memory ability. This study investigated white matter microstructure of the medial MFB , specifically the supero‐lateral branch (sl MFB ), following TBI , and its association with performance on attention and working memory tasks. Method Neuropsychological measures of attention and working memory were administered to 20 moderate‐severe participants with TBI (posttraumatic amnesia M = 40.05 ± 37.10 days, median time since injury 10.48 months, range 3.72–87.49) and 20 healthy controls. Probabilistic tractography was used to obtain fractional anisotropy ( FA ) and mean diffusivity ( MD ) values for 17 participants with TBI and 20 healthy controls. Results When compared to controls, participants with TBI were found to have significantly lower FA ( p < .001) and higher MD ( p < .001) sl MFB values, and they were slower to complete tasks including Trail Making Task‐A, Hayling, selective attention task, n ‐back, and Symbol Digit Modalities Test. Conclusion This study was the first to demonstrate microstructural white matter damage within the sl MFB following TBI . However, no evidence was found for an association of alterations to this tract and performance on attentional tasks.