Event-related potential indices 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.

Persistent visuospatial attention deficits following mild head injury in Australian Rules football players.

The ability to direct visuospatial attention covertly was studied in two groups of Australian Rules football players who had sustained mild head injuries (MHI) during competition. Their performance was compared to 12 non-injured sportsmen using a cued reaction time (RT) task which measured the RT benefit of valid directional cueing and the RT cost of miscueing. In Experiment 1, nine footballers tested within 2 weeks of sustaining their injury showed the same cost as normals in speed of response to targets in the unexpected visual field. However, their responses to targets in the expected location (following valid cues) showed only a minor benefit compared to controls. Moderate to severely injured patients also show a normal cost but a reduced or absent benefit (Cremona-Meteyard and Geffen, Neuropsychologia 30, 123-132, 1992). When subjects were retested 1 year later their pattern of performance had not altered but overall RT had improved. Experiment 2 replicated these findings in another eight footballers tested at least 1 year after sustaining their MHI. A persistent consequence of MHI might be an inability to take action quickly in response to expected events.

Covert orientation of visual attention after closed head injury.

The ability to orient visual attention covertly was studied in 11 patients who had suffered a moderate or severe closed head injury (CHI) at least 1 year previously. Their performance was compared to nine matched controls using a cued reaction time (RT) task which measured the RT benefit of valid directional cueing and the RT cost of miscueing. The CHI and control groups did not differ in overall RT. Relative to controls, the CHI group showed normal cost but hardly any benefit, indicating that the normal capacity to pre-align attention with a cued location was impaired.