Clustering and switching in verbal fluency in Parkinson's disease

Thirteen patients with non-dementing Parkinson's disease (PD) were compared with 11 healthy controls on a semantic and a phonemic verbal fluency task. Analysis of the data examined total words produced as well as two addition al components of verbal fluency: Clustering (generating words which share a semantic or phonemic similarity), and switching (the ability to shift betw een clusters). Overall, PD patients generated fewer words than the controls , and made less use of switching both in the phonemic and semantic fluency tasks. They did not differ from the controls in the amount of clustering. T he results are consistent with the notion that patient groups in which the frontal lobes are compromised will perform poorly on switching tasks.