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May 1994

Brain Potentials Reveal Deficits of Language Processing After Closed Head Injury

Arch Neurol. 1994;51(5):482-493. doi:10.1001/archneur.1994.00540170058017

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.