The long-term effects of traumatic brain injury on the coordinative function of the central executive.

The objective of this study was to compare the coordinative function of the central executive of working memory in matched groups of controls and persons with traumatic brain injury (TBI) with long-term impairments in functioning, using a dual-task paradigm. The dual-task procedure required participants to complete digit span and tracing tasks separately and then together to produce a change index that reflects loss of productivity on the dual trial. A TBI group and a matched group of controls were compared on this task and on ratings of social competency and neuropsychological tests. The two groups were found to differ in social competence, in the number of dysexecutive symptoms, and on dual-task performance, but not on any other measures of cognitive ability. Poor performance on the dual task was found only in persons with initial very severe TBI. There was no evidence that the group difference on the dual task was the consequence of increased task difficulty level, distribution of attention, or other within-task biases. Performance on the dual task was correlated with dysexecutive symptoms and social competency (in particular interpersonal and cognitive competence), but not with other tests of executive functioning. The findings suggest that deficits in the coordinative function persist in long-term survivors of TBI after other deficits in executive functioning may have resolved and are associated with lower ratings of current interpersonal competence.