Brain Potentials Reveal Deficits of Language Processing After Closed Head Injury

Objective: To delineate deficits in language processing after closed head injury with use of behavioral measures and event-related brain potentials. Design: Case-control design. All subjects participated in three verbal event-related brain potential experiments, and the resulting measures were compared both within and between groups. Patients/Controls: Eleven patients at least 2 years after severe closed head injury (Glasgow Coma Scale score <8 at admission and duration of posttraumatic amnesia >48 hours) were compared with a control group matched for age and educational level. Interventions: None. Main Outcome Measures: Reaction times and percentage correct as behavioral measures in the three experiments (sentence verification, semantic and repetition priming with lexical decision task, and continuous word recognition). Event-related brain potentials were quantified by area measures in successive time windows for the different experimental conditions and for different experiments. Results: The reaction times of the patient group were significantly longer than those of the controls (P<.005). Similarly, the patients' accuracy was significantly worse in all experiments (P<.03). The event-related brain potentials of the controls showed a clear and significant reduction of a negative component (N400) to terminal words of true sentences (sentence verification experiment),semantically primedwords and repeated words (lexical decision experiment), and recognized words (continuous word recognition). For the patients, a clear N400 effect was seen only in the sentence verification task (delayed by about 100 milliseconds), while only later event-related brain potential modulations were seen in the other tasks. Conclusion: Language functions are disturbed after closed head injury. The electrophysiologic data suggest difficulties in the integration of incoming linguistic stimuli with the previous context as a possible underlying cause.