Divided attention in brain-injured patients.

Clinical observations have shown that brain-injured patients perform poorly in tasks requiring attention. While selective and sustained attention has been extensively investigated, there is little systematic information on how brain-injured patients perform on divided attention tasks requiring simultaneous handling of and responding to two sources of information. This study was designed to analyse the behavior of hospitalized brain-injured patients as compared with matched normal controls in performing a dual task consisting of pursuit motor tracking coupled with delayed digit recall (DDR). Four two-minute trials were given. Time on target (TOT) and number of recall errors were recorded. It was assumed that the brain-injured group would (a) have lower TOT and more recall errors; and (b) show less learning effect. Results confirmed both expectations: (1) for the brain-injured group, TOT was lower and did not improve across trials; moreover, the number of recall errors was higher, increasing across trials; (2) for the control group, the number of recall errors was negligible across trials and TOT improved with time; (3) the normal trade-off between two simultaneous difficult tasks was not observed in the brain-injured group as they failed in both tasks; (4) the number of recall errors of the brain-injured subjects markedly increased towards the end of each trial, suggesting rapidly increasing fatigue. Thus, brain-injured patients appeared limited not only in their attention capacity but also in the variety of strategies they employ in processing information.