Traumatic Brain Injury

Accumulating evidence suggests that individuals with a history of multiple traumatic brain injuries (TBIs) are at increased risk for developing post-traumatic stress disorder (PTSD) when compared to trauma exposed individuals without a TBI history. These findings, coupled with the overwhelming prevalence of blast-related TBI endured by American soldiers in current military theatres, highlight the urgent need to investigate processes linking TBI with elevated risk for PTSD. Research has indicated a variety of executive functioning deficits associated with TBI that point towards prefrontal cortex dysfunction similar to those observed among individuals at risk for PTSD. These deficits have been linked to PTSD through fear conditioning and extinction paradigms, in which those with greater fear conditioning and/or deficient fear extinction are at increased risk for PTSD. The current study was the first to investigate fear conditioning and extinction abnormalities as putative mechanisms explaining the link between TBI history and risk for PTSD. Results indicated that individuals with a history of TBIs did not exhibit aberrations in rates of fear conditioning or extinction. However, a history of TBIs was associated with greater overall reactivity throughout each phase of the protocol. Interestingly, individuals with a history of TBIs also demonstrated slowed habituation of reactivity to the unconditioned stimulus, though this effect was trending. These results suggest that TBI may be linked with PTSD not through rates of fear conditioning and extinction, but through greater reactivity to novel and potentially threatening stimuli as well as slowed habituation to aversive stimuli.