EVENT-RELATED POTENTIAL INDEXES OF VISUAL-ATTENTION FOLLOWING MODERATE TO SEVERE CLOSED-HEAD INJURY

Covert orientation of visual attention was studied in eight closed head injury (CHI) subjects who fixated warning cues and pressed a button at peripheral target onset. Directional cues (arrows) indicated the most probable (p=0.8) side of target occurrence while neutral cues (crosses) gave no directional information. A NoGo cue (vertical bar) indicated no response was required. Compared to eight matched controls the CHI subjects displayed slowed processing of all cues (increased P2, N2 and P3 latencies). Also, evidence was found for very early impairment (increased P2 amplitude) in directing attention. Further, the CHI group did not show the normal attenuated CNV after NoGo signals, suggesting perseverative behaviour. Finally, the amplitude and latency of the P3 component (post-cue and post-target) approached normal as time since injury increased.