Distinguishing TBI Malingering and Fatigue Using Event-Related Potentials

Poorer-than-expected performance on cognitive-behavioral tasks may indicate malingering, or it could be an outcome of fatigue, resulting in false positives when suboptimal task performance is used to flag individuals feigning or exaggerating symptoms of traumatic brain injury (TBI). The primary goal of this study was to examine the P3 event-related potentials (ERP) and behavioral outcomes associated with TBI malingering and fatigue, in order to distinguish between them. A secondary goal was to determine if history of TBI (hTBI) is associated with differences in fatigue, ERPs, or performance on a short-term memory task. Participants completed the Mental Fatigue and Related Symptoms (SR-MF) questionnaire and were interviewed to assess TBI history, then they completed a computerized "old/new" (match-mismatch) task while ERPs were recorded, under three conditions: Normal, Malinger, and Fatigue. Participants reported mild fatigue at the end of study, with no difference between individuals reporting a history of TBI (n = 32) and healthy controls (n = 47). Fatigue was associated with prolonged P3 latency but was otherwise indistinguishable from Normal. In contrast, Malinger was clearly distinguished from Normal by significantly lower accuracy, longer reaction times, reduced P3 amplitude on Match trials, and a smaller old/new ERP effect. Individuals with a history of TBI reported clinical levels of fatigue at baseline but did not differ significantly from healthy controls on any behavioral or ERP measure. The results support the use of behavioral and ERP measures to identify malingering, without concern over confounding effects of mild subjective fatigue, including mild fatigue induced by testing.