Verbal and design fluency in patients with frontal lobe lesions

The ability to generate items belonging to categories in verbal fluency tas ks has been attributed to frontal cortex. Nonverbal fluency (e.g., design f luency) has been assessed separately and found to rely on the right hemisph ere or right frontal cortex. The current study assessed both verbal and non verbal fluency in a single group of patients with focal. frontal lobe lesio ns and age- and education-matched control participants. In the verbal fluen cy task. participants generated items belonging to both letter cues (F, A, and S) and category cues (animals and boys names). In the design Fluency ta sk, participants generated novel designs by connecting dot arrays with 4 st raight lines. A switching condition was included in both verbal and design fluency tasks and required participants to switch back and forth between di fferent sets (e.g., between naming fruits and furniture). As a group, patie nts with frontal lobe lesions were impaired, compared to control participan ts, on both verbal and design fluency tasks. Patients with left frontal les ions performed worse than patients with right frontal lesions on the verbal fluency task, but the 2 groups performed comparably on the design fluency task. Both patients and control participants were impacted similarly by the switching conditions. These results suggest that verbal fluency is more de pendent on left frontal cortex, while nonverbal fluency tasks, such as desi gn fluency, recruit both right and left frontal processes.