Parkinson’s disease (PD) is characterized by dopamine deficiency and subsequent motor symptoms including bradykinesia and tremor.  Motor symptoms have an asymmetrical clinical presentation early in the disease process relative to contralateral dopaminergic cell loss.  Asymmetrical hemispheric dysfunction can contribute to different cognitive deficits including executive function, visuospatial ability, language, and other domains.  This investigation centered on the Design Fluency measure due to its sensitivity to right hemispheric dysfunction.  We hypothesized that PD subjects, in particular, those with left motor symptoms, would produce fewer novel designs and incur more errors.

Design fluency task performances by 60 right-handed non-demented PD subjects equally separated by right (PDR) and left (PDL) symptom onset were compared to productions from a matched group of 30 control subjects.  Parkinson's disease groups were also matched on clinical measures (e.g. Hoen & Yahr, LEDD).  Novel designs and error types (repetitions and set-loss errors, including incomplete designs) were accounted for.  Statistical comparisons were controlled for the effects of depression and bradykinesia.

PD groups and controls did not differ on the number of novel designs generated in any trial (p > .05).  PDL subjects, however, generated more designs having fewer lines than stipulated in comparison to the other groups (p = .032).  Effects of bradykinesia and depression were not significant to this finding, implicating an underlying cognitive element.

"Incomplete design" set-loss errors were more frequent in the PDL group.  This error type is likely due to visual and motor planning difficulties caused by striatal degeneration of the right hemisphere and suggests problems with self-monitoring and an inability of these subjects to adjust motor programming online.  Our results have rehabilitative implications specific to PD left motor symptoms.