Functional MRI of mild traumatic brain injury (mTBI): progress and perspectives from the first decade of studies

Abstract

Mild traumatic brain injury (mTBI) represents the great majority of traumatic brain injuries, and is a common medical problem affecting cognitive and vocational functioning as well as quality of life in some individuals. Functional MRI (fMRI) is an important research method for investigating the neuroanatomic substrates of cognitive disorders and their treatment. Surprisingly, however, relatively little research has utilized fMRI to examine alterations in brain functioning after mTBI. This article provides a critical overview of the published fMRI research on mTBI to date. These topics include examination of frontal lobe/executive functions such as working memory, as well as episodic memory and resting state/functional connectivity. mTBI has also been investigated in military populations where studies have focused on effects of blast injury and comorbid conditions such as post-traumatic stress disorder and major depressive disorder. Finally, we address fMRI evaluations of response to behavioral or pharmacological challenges and interventions targeting cognitive and behavioral sequelae of mTBI. The review concludes with identification and discussion of gaps in current knowledge and future directions for fMRI studies of mTBI. The authors conclude that fMRI in combination with related methods can be expected to play an increasing role in research related to studies of pathophysiological mechanisms of the sequelae of mTBI as well as in diagnosis and treatment monitoring.

Fig. 1

Verbal N-back task design showing 0-back, 1-back, 2-back, and 3-back conditions

Fig. 2

Typical bifrontal and biparietal working-memory task-related activation for 3-back>0-back condition in a group of 35 healthy adult control participants

Fig. 3

Regions of increased activation in working memory circuitry (3-back>0-back) as a function of COMT genotype (met/met>any val) in 40 individuals (27 with mTBI, 13 healthy controls)