THE EFFECTS OF VISUAL DISTRACTION FOLLOWING TRAUMATIC BRAIN INJURY

Clinical assessments of individuals with traumatic brain injury (TBI) typically report attentional difficulties, with distractibility promin ent among these complaints. However, laboratory-based measures have of ten failed to find disproportionate distraction among patients with TB I, as compared to control participants. In this experiment, we tested 21 patients hospitalized for rehabilitation following recent TBI and 2 1 demographically comparable control subjects on a visual reaction tim e go-no-go task in which the target was preceded or followed by a brig htly colored moving visual stimulus, appearing above the target locati on. Early distracters actually served as warning stimuli, improving ac curacy and speed for both participant groups. Distracters occurring at or shortly after the time of target presentation had no significant i mpact on accuracy or response bias in either group, but did produce sl owing of RT that was significantly greater for patients than for contr ols. The distracter that produced maximal slowing occurred 100 ms afte r the presentation of the target or foil. Repeated testing sessions le d to reduction in the impact of the distracter and loss of the group d ifference in RT impact. The degree of RT slowing induced by distractio n was modestly related to injury severity, as measured by the current score on the Disability Rating Scale, and the time until the patient f irst followed verbal commands. There was also a trend of greater RT sl owing among individuals with focal orbitofrontal lesions, as assessed on neuroimaging studies. These results document a greater susceptibili ty to extraneous visual distraction among patients with TBI in compari son to controls. The fact that this difference appears only in the RT domain, and is greatest when the distracter follows the target, sugges ts that the primary impact of visual distracters is on response prepar ation and execution rather than target detection.