Divided and focused attention in patients with lesion of the prefrontal cortex.

Despite the common claim of attention disorders in patients with frontal lobe lesion, attention has been poorly investigated and its contribution to behavioral changes has not been studied. The aim of this study was to assess divided (Experiment I) and focused attention (Experiment II) in patients with prefrontal damage. The study used simple detection tests measuring reaction times (RT) to successive stimuli of one modality and of randomly varying modalities (divided attention) and Go No-Go tests (focused attention). Experiment I showed that RT difference between patients and controls increased when stimuli modality was uncertain, a result we attributed to a deficit of divided attention. Experiment II showed that patients remained sensitive to irrelevant stimuli, demonstrating their inability to focus attention. The prominent behavioral change in patients consisted of increased distractibility which was correlated with divided and focused attention deficits. Finally, the presence on magnetic resonance imaging of a left lesion in the superior part of the prefrontal cortex and in the head of the caudate nucleus was the best predictor of attention disorders. In conclusion, this study shows that patients with a prefrontal lesion suffer from divided and focused attention deficits that correspond to behavioral changes.