Hemispheric and executive influences on low-level language processing after traumatic brain injury.

Objective: The purpose of this study was to examine whether minor high-level language deficits found after traumatic brain injury (TBI) might be due to low-level language processing issues or executive control influences. A possible mechanism was also investigated.

Method: Nineteen age- and education-matched healthy controls (16 M, 3 F) and 19 persons who had experienced a complicated mild, moderate or severe TBI between 1-3 years prior (16 M, 3 F; mean GCS = 9.44) participated in two computerized behavioural experiments utilizing two paradigms standard in the psycholinguistic literature (priming with lexical decision and verb generation), which included trials of greater and lesser executive demand.

Results: Response time and accuracy differences were found in both experiments, indicating deficits in single-word processing for the patient group. Disproportionate difficulty was found for trials which included an executive component. Right visual field (left hemisphere) preferences were found to be stronger in the TBI group than in controls.

Conclusions: Results suggest that persons with TBI may have difficulties in processing single words alone, especially under conditions of increased executive demand, and that atypical patterns of hemispheric recruitment may be associated with these difficulties.