Seventy-four patients with focal brain lesions
were compared to a neurologically normal control group
on tasks of letter-based and category-based list generation.
When patients were divided only by right frontal, left
frontal, or nonfrontal lesion sites, the pattern of fluency
impairments confirmed prior claims. When more precise lesion
sites within the frontal lobes were compared between groups
classified based on their fluency performance, much more
specific brain–behavior relations were uncovered.
Damage to the right dorsolateral cortical or connecting
striatal regions, the right posterior area, or the medial
inferior frontal lobe of either hemisphere did not significantly
affect letter-based fluency performance. Superior medial
frontal damage, right or left, resulted in moderate
impairment. Patients with left dorsolateral and/or striatal
lesions were most impaired. Left parietal damage led to
performance relatively equivalent to the superior medial
and left dorsolateral groups. The same lesion sites produced
impairments in category based fluency, but so did lesions
of right dorsolateral and inferior medial regions. Task
analysis and correlations with other measures revealed
that different cognitive processes related to different
brain regions underlie performance on verbal fluency tests.
(JINS, 1998, 4, 265–278.)