Interference in dual-fluency tasks after anterior and posterior cerebral lesions.

According to earlier findings, letter fluency, repetitive pattern drawing and figural fluency are more sensitive to anterior than to posterior brain lesions. The aim of this study was to demonstrate that the percentage impairments from the single-task results are more pronounced after anterior than after posterior lesions when letter fluency is performed simultaneously with pattern drawing or figural fluency. The single-task results showed no significant differences between the patients with anterior and posterior lesions. The patients with anterior lesions, especially those with left-anterior lesions, had more pronounced percentage dual-task impairment than the other patients in letter fluency but not in pattern drawing or figural fluency. The results did not confirm the prediction that the average of the percentage decrements of the concurrent performances (the combined dual-task cost) or the larger of the two decrements would be more pronounced after anterior than posterior lesions. However, the patients with left-hemisphere lesions were inferior to those with right-hemisphere lesions in the single letter-fluency task, and the combined dual-task cost was more pronounced after left-hemisphere lesions.