The ability to generate items belonging to categories in verbal
fluency tasks has been attributed to frontal cortex. Nonverbal
fluency (e.g., design fluency) has been assessed separately
and found to rely on the right hemisphere or right frontal cortex.
The current study assessed both verbal and nonverbal fluency
in a single group of patients with focal, frontal lobe lesions
and age- and education-matched control participants. In the
verbal fluency task, participants generated items belonging
to both letter cues (F, A, and S)
and category cues (animals and boys' names). In the design
fluency task, participants generated novel designs by connecting
dot arrays with 4 straight lines. A switching condition was
included in both verbal and design fluency tasks and required
participants to switch back and forth between different sets
(e.g., between naming fruits and furniture). As a group, patients
with frontal lobe lesions were impaired, compared to control
participants, on both verbal and design fluency tasks. Patients
with left frontal lesions 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 dependent on left frontal cortex, while nonverbal
fluency tasks, such as design fluency, recruit both right and
left frontal processes. (JINS, 2001, 7,
586–596.)
Recruiting the right hemisphere: Sex differences in inter-hemispheric communication during semantic verbal fluency
