Closed head injury-related information processing deficits: an event-related potential analysis

Event-related potentials (ERPs) can elucidate aspects of sensory and cognitive processing that have been compromised due to closed head injury. We present the results of two investigations, one previously unreported, in which we used ERPs to evaluate information processing in head-injury survivors. In the first study, we used visual and auditory reaction time tasks differing in attentional demands to assess processing after head trauma. We found numerous changes in auditory processing in survivors: longer reaction times (but normal accuracy), longer N200 and P300 latencies, and reduced N100 and N200 amplitudes. In contrast, on visual tasks, only reduced N200 amplitude distinguished survivors and controls. To increase attentional demands, in a second study, we administered the continuous performance test (CPT). Survivors performed with lower accuracy than controls on visual and auditory tasks, and their ERPs were characterized by smaller visual and auditory N200s and P300s and smaller auditory N100s. We also present a synthesis, derived from a review of the literature, of closed head-injury effects on ERPs. Our own findings are in agreement with that synthesis. Namely, cognitive ERP components are more sensitive than sensory components to the effects of trauma. Specifically, in survivors, the amplitudes of N200 and P300 are often reduced, and their latencies prolonged. In general, as compared with visual ERPs, auditory ERPs may be more susceptible to the effects of closed head injury, suggesting that the auditory processing system is more vulnerable than the visual system. We conclude by discussing the potential use of ERPs to monitor clinical course and recovery in survivors of closed head injury.