Cognitive control in mild traumatic brain injury: conflict monitoring and conflict adaptation.

Recent studies suggest that individuals who have experienced a concussion or mild traumatic brain injury (TBI) show deficits in cognitive control. We tested the hypothesis that behavioral (response time [RT] and error rate) and electrophysiological (N450 and conflict SP components of the event-related potential [ERP]) reflections of conflict monitoring and conflict adaptation would be attenuated in 29 individuals with mild TBI compared to 36 control participants. Groups did not differ in age, sex, years of education, or neuropsychological test performance. Conflict monitoring and conflict adaptation can be seen when behavioral and ERP indices are reduced following high-conflict trials relative to low-conflict trials. Participants completed a Stroop task with 50% congruent and 50% incongruent trials. Behaviorally, both groups showed statistically significant conflict adaptation effects for RTs and error rates; these effects did not differ as a function of group. For ERPs, both groups showed more negative N450 and more positive conflict SP amplitudes on incongruent trials relative to congruent trials. Groups significantly differed in level of conflict adaptation for the conflict SP; controls showed significant conflict adaptation, whereas individuals with mild TBI did not. ERP amplitudes did not correlate with indices of injury severity or time since injury. Findings replicate and extend previous work that suggests the conflict SP is sensitive to conflict adaptation in healthy individuals, but is decreased in individuals across the range of TBI severity. Findings also suggest that mild TBI is associated with intact conflict monitoring, but altered conflict adaptation and adjustment processes.