Primary objective: Investigation of the impact of traumatic brain injury (TBI) on the functional brain network that mediates working memory function.
Research design: Functional magnetic resonance imaging (fMRI) during an n-back working memory task in nine chronic-stage patients with TBI and nine age-matched healthy controls. In addition to classical analyses investigating regional activity, the authors examined functional connectivity of the brain regions critical to working memory performance using psychophysiological interaction (PPI) analyses.
Main outcomes and results: Patients with TBI made a greater percentage of errors than controls at high working memory load conditions. The fMRI data showed that the activation of the left inferior parietal gyrus (LIPG) was significantly reduced, whereas the activation of the right inferior frontal gyrus (RIFG) was significantly increased in patients compared with controls. Task performance accuracy was significantly associated with the activation of the LIPG in controls and the activation of the RIFG in patients. PPI analyses on fMRI data further suggested that the functional connectivity between the RIFG and LIPG was compromised in patients.
Conclusion: The abnormal functional connectivity between LIPG and RIFG may underlie the observed working memory deficits and abnormal brain activation pattern in patients.