BRAIN POTENTIALS REVEAL DEFICITS OF LANGUAGE PROCESSING AFTER CLOSED-HEAD INJURY

Objective: To delineate deficits in language processing after closed h ead injury with use of behavioral measures and event-related brain pot entials. Design: Case-control design. All subjects participated in thr ee verbal event-related brain potential experiments, and the resulting measures were compared both within and between groups. Patients/Contr ols: Eleven patients at least 2 years after severe closed head injury (Glasgow Coma Scale score < 8 at admission and duration of posttraumat ic 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 t hree experiments (sentence verification, semantic and repetition primi ng with lexical decision task, and continuous word recognition). Event -related brain potentials were quantified by area measures in successi ve time windows for the different experimental conditions and for diff erent experiments.Results: The reaction times of the patient group wer e significantly longer than those of the controls (P < .005). Similarl y, 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 term inal words of true sentences (sentence verification experiment), seman tically primed words 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 bra in potential modulations were seen in the other tasks. Conclusion: Lan guage functions are disturbed after closed head injury. The electrophy siologic data suggest difficulties in the integration of incoming ling uistic stimuli with the previous context as a possible underlying caus e.