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Patients with severe traumatic brain injury (TBI) often demonstrate impairments in performance monitoring—an evaluative control process that can be measured using the error-negativity/error-related negativity (Ne/ERN) and post-error positivity (Pe). The Ne/ERN and Pe are event-related potential (ERP) components generated following errors, with current theories suggesting the Ne/ERN reflects automatic performance monitoring and the Pe reflects error processing and awareness. To elucidate the electrophysiological mechanisms of performance monitoring deficits following severe TBI, behavioral and ERP measurements were obtained, whereas participants with severe TBI and neurologically-healthy comparison participants performed a modified color-naming version of the Stroop task. Behaviorally, both groups demonstrated robust response-time (RT) and error-rate interference. Participants with TBI exhibited generalized RT slowing; no significant between-groups interactions were present for RTs or error rates. ERP results indicate Ne/ERN amplitude was attenuated in participants with TBI, whereas the pattern of Pe amplitude did not clearly differentiate groups. Findings suggest the Ne/ERN as a potential electrophysiological marker of evaluative control/performance monitoring impairment following TBI. Implications for future research and potential clinical application as well as potential limitations in conducting electrophysiological research in neurologically-impaired populations are discussed. (JINS, 2007,13, 961–971.)

Many rehabilitation protocols following traumatic brain injury (TBI) utilize reinforcement and reward to influence behavior and facilitate recovery; however, previous studies suggest survivors of severe TBI demonstrate impairments in contingency utilization and sensitivity. The precise neurobiological mechanisms underlying these deficits have not been thoroughly explored, but can be examined using the “feedback-related negativity” (FRN)— an event-related potential (ERP) component evoked following performance or response feedback (e.g., whether a monetary reward is obtained) with a larger FRN following unfavorable than favorable outcomes—particularly when unfavorable feedback occurs in the context of high reward probability. We examined ERPs elicited by favorable (monetary gain: “reward”) and unfavorable (no monetary gain: “non-reward”) feedback during a guessing task where probability of reward outcome was manipulated in survivors of severe TBI and demographically matched healthy participants. Consistent with previous findings, controls showed larger amplitude FRN to non-reward feedback and the largest amplitude FRN following a non-reward when reward probability context was greatest. In contrast, FRN in TBI participants did not significantly differentiate non-reward from reward trials and their FRN was largest to reward trials in the low reward probability context. Findings implicate an electrophysiological marker of impaired reward context sensitivity following severe TBI. (JINS, 2007, 13, 615–625.)

Some critically ill patients have dramatic recollections of the intensive care unit (ICU), whereas 23-50% have little or no recollection of their ICU stay. In addition, cognitive impairments are common following critical illness and ICU treatment. Little is known regarding the relationship between cognitive sequelae and ICU recall. We assessed recall of the ICU and its relationship to cognitive functioning at hospital discharge and 1 and 2 years after discharge in 70 consecutive acute respiratory distress syndrome (ARDS) patients. Seventeen patients (24%) had no recall of the ICU. Patients without ICU recall had increased rates of cognitive sequelae at hospital discharge and 1-year follow-up compared with the ICU recall group. Patients without ICU recall had a greater magnitude of cognitive impairments at hospital discharge, but not at 1- or 2-year follow-up. Profile analysis showed significant group differences in general intellectual functioning, executive function, processing speed, and spatial skills at hospital discharge, but not at 1- or 2-year follow-up. Estimated premorbid intelligence scores were inversely related to the magnitude of cognitive sequelae, suggesting greater "cognitive reserve" in patients with fewer cognitive decrements.