SUSTAINED AROUSAL AND ATTENTION AFTER TRAUMATIC BRAIN INJURY

Clinicians report that patients with traumatic brain injury (TBI) ofte n have difficulty with tasks requiring sustained attention, and there are neuroanatomical and neurophysiological reasons to expect such defi cits. Nevertheless, laboratory measures of sustained attention or vigi lance in TBI have produced conflicting results. These inconsistencies may be due to patient heterogeneity as well as the fact that vigilance performance is dependent on highly specific features of the task desi gn. We developed a visual vigilance task in which the influence of non -attentional factors was minimized and task difficulty for patients an d controls made comparable. Performance was characterized with respect to vigilance level as well as vigilance decrement, using measures of perceptual discrimination, response bias, reaction time and reaction t ime variability. Twenty-six patients with recent TBI and 18 control su bjects were tested on this task. A MANOVA of ranked scores revealed si gnificantly different patient and control performance overall. Initial level of performance (vigilance level) was slower and more variable f or patients than controls, and patients showed more conservative respo nse biases. Deterioration over time (vigilence decrement) was also ste eper for patients than controls for reaction time, reaction time varia bility, and response bias. Deterioration in accuracy (D') did not diff er significantly between patients and controls. Performance was not re lated to available measures of injury severity. Hypotheses relating ar ousal mechanisms to vigilance performance are discussed.