PHASIC AROUSAL IN RESPONSE TO AUDITORY WARNINGS AFTER TRAUMATIC BRAININJURY

Traumatic brain injury (TBI) is believed to have adverse effects on at tention, but because of the multifaceted nature of the arousal and att entional network, the precise impact of TBI on various subcomponents o f this network remains controversial. As part of a larger program of r esearch on attention in TBI, we studied the effects of auditory warnin g signals on accuracy, reaction time, and response bias, as indices of phasic arousal in a visual go/no-go task. Warnings were presented ran domly at various pre-stimulus intervals to a sample of recently injure d patients and control subjects. For each subject and performance inde x, we examined the time interval required to reach maximal phasic arou sal, the degree of performance change occurring at this maximal point, and the ability to maintain this state of increased arousal over long er warning intervals. After adjustment for baseline differences, there were no significant differences between patients and controls in any aspect of performance. Examination of effect sizes suggested that this was not due to limited statistical power, but that any differences be tween groups, if present, must have been small. In contrast, in our pr ior research on sustained attention and observable behaviors related t o attention, large group differences have been found. These data sugge st that mechanisms responsible for auditorily-induced phasic arousal r esponses are largely preserved in severe TBI. (C) 1997 Elsevier Scienc e Ltd.