Structural brain correlates of verbal fluency in Parkinson's disease.

Verbal fluency tests are often used to assess cognitive dysfunction in Parkinson's disease. These tests have been found to be impaired even in initial stages of this illness. We applied voxel-based morphometry to investigate the neuroanatomic substrates of semantic and phonemic fluency impairment. Correlations between gray matter density and semantic as well as phonemic fluency performance were performed in 32 nondemented Parkinson's disease patients. We found that gray matter of temporal, frontal and cerebellar areas correlated with semantic fluency scores. In contrast, no gray matter correlations were found for phonemic fluency or for general cognitive functions. These results suggest that semantic fluency impairment is reflecting structural gray matter changes in regions involved in language networks.