Long-latency event-related potentials after mild traumatic brain injury

Abstract

This study was an investigation of early changes in long latency event-related potentials with an emphasis on the N200/P300 complex in a group of adults with mild traumatic brain injury (TBI). Subjects with mild TBI and a matched group of non-injured subjects were presented three auditory oddball tasks differing in degree of difficulty. Subjects with TBI were tested within 100 hours of the injury and again at 20 days post-injury. Non-injured subjects also underwent two test sessions, with visit two occurring 18 days after visit one. Event-related potentials were recorded from three midline sites (Fz, Cz, Pz) during the three oddball tasks, two tone-frequency discrimination tasks and one tone-duration discrimination task. The amplitude and latency of both the N200 and the P300 were compared between the two groups. The amplitudes of the two components did not differ significantly between the two groups. However, the latencies of both the N200 and the P300 were prolonged in the mild TBI group. This delay interacted significantly with recording site, with the maximal between-group difference occurring at Fz for both components. The group effect did not interact significantly with the timing of the test session or the difficulty of the oddball task. Taking the latencies of the two components as indices of information processing speed, the data suggest the presence of reduced processing speed in the mild TBI group that persists for at least three weeks post-injury. Increasing task difficulty, at least to the level used in the present study, did not enhance the observed difference between the two groups. The findings related to recording site are consistent with neurobehavioral, neuroimaging, and pathophysiological data which indicate greater effects of injury on frontal regions of the brain.