Electrophysiologic abnormalities of auditory and visual information processing in patients with traumatic brain injury.

OBJECTIVE: Through both auditory and visual modalities, we sought to explore the efficacy of event-related potentials in detecting residual cognitive impairments in patients with traumatic brain injury (TBI).
DESIGN: Control subjects and TBI patients with favorable recovery were recruited. Pure tone and primary color discrimination tasks were utilized to elicit auditory and visual event-related potentials, respectively. All subjects were instructed to push a response button when they detected the target stimuli. Both behavioral and electrophysiologic responses were obtained simultaneously. We analyzed the event-related potential waveforms and examined the differences in amplitude, latency, behavioral reaction time, and response accuracy.
RESULTS: A total of 11 TBI patients and 11 control subjects were tested. Results showed that (1) TBI patients had significantly lower P300 amplitude in both auditory (11.2 vs. 22. 7 microV) and visual (11.6 vs. 20.9 microV) domains, (2) TBI patients had significantly longer P300 latency in both auditory (355 vs. 294 msecs) and visual (376 vs. 341 msecs) modalities, and (3) although there was no significant difference in response accuracy (97.7%vs. 100%), reaction time for both auditory and visual tasks were significantly longer in TBI patients (auditory, 404 vs. 277 msecs; visual, 397 vs. 346 msecs).
CONCLUSION: Although TBI patients with good recovery showed similar response accuracy when compared with control subjects, they demonstrated significantly poorer performance in both electrophysiologic and behavioral responses. Diminished amplitudes and prolonged latencies in P300 responses indicate impaired organization and categorization of incoming sensory information; prolonged behavioral reaction times suggest slowing in the response execution process. Clinical and theoretical implications and goals for continued research are discussed.