Working memory and supervisory control after severe closed-head injury. A study of dual task performance and random generation.

Survivors of severe closed-head injury (CHI) frequently suffer from slowed information processing. Whether supervisory strategies are additionally impaired remains a point of debate. The first part of this study employed a self-paced dual task; the second part, a random generation task, performed at a paced rate, under single and dual task conditions. A measure of information processing speed was used as a covariate in statistical analysis. In the first experiment, in addition to slow processing, patients performed slightly poorer than controls on each task. In the second experiment, patients' performance (one randomness index in single task condition, and processing of dual task) was impaired even after statistical control of slow processing. These results suggest that there is at least some degree of impairment in supervisory strategies in addition to, but independent of, slowed processing. The clinical significance of this finding is discussed.