Understanding quantitative and qualitative figural fluency in patients with Parkinson's disease.

Figural fluency refers to the ability to internally generate appropriate non-verbal behaviour. Whereas deficits in verbal fluency rank among the most prominent cognitive sequelae in Parkinson's disease (PD), little is known about figural fluency and its assessment in PD. This is the first comprehensive comparison of the psychometric properties of figural fluency tasks in PD. PD patients (n = 22) and matched normal controls (n = 27) were compared in widely used figural fluency measures. The ability to assess PD-specific cognitive morbidity was assessed via comparison with a matched neurological sample of various aetiologies (n = 22). Construct validity was assessed by means of linear regression analyses of figural fluency measures and an extensive cognitive test battery. PD patients were impaired in all measures of figural fluency tasks. PD-specific impairments were identified regarding perseverative and strategic behaviour. Importantly, only perseverative, but not repetitive, behaviour was able to identify PD-specific cognitive morbidity. Quantitative fluency can be predicted by basic cognitive functions (e.g. visuospatial ability, visuomotor speed) as well as other measures of executive functioning. However, qualitative test scores, especially of the Five-Point Test (FPT), yield important and additional diagnostic information in PD. Qualitative test parameters of figural fluency measures, especially of the FPT, offer the unique possibility to assess PD-specific cognitive impairments in the areas of perseverative and strategic behaviour.