Impairment only on the fluency subtest of the Frontal Assessment Battery after prefrontal lesions

The Frontal Assessment Battery is a set of six subtests that is used widely to assess frontal cortical executive dysfunction. Performance on the Frontal Assessment Battery has been shown to be sensitive to various neurodegenerative diseases, but it has never been shown to be sensitive to damage restricted to the frontal cortex. Thus, despite its wide use, it has never been validated on an appropriate population of patients with frontal lesions. The present study shows that, of the six subtests that comprise the Frontal Assessment Battery, only performance on the verbal fluency subtest (mental flexibility) was specifically sensitive to injury restricted to the frontal cortex. Performance of patients with damage to the dorsal part of the medial frontal region in the language-dominant left hemisphere was impaired. None of these patients was aphasic at the time of testing. The critical region in the dorsomedial frontal cortex includes the supplementary speech zone but is not restricted to it: it extends into the cingulate motor region and the paracingulate cortex as well as the medial prefrontal areas 8 and 9. The results indicate that the Frontal Assessment Battery is not a sensitive measure of prefrontal cortical dysfunction, except for the verbal fluency subtest.