Impairment of semantic knowledge in Parkinson disease

Background: Parkinson disease (PD) is commonly characterized by cognitive d eterioration, but it is still unclear whether PD is associated with semanti c impairments. Objective: To evaluate semantic knowledge of concepts in patients with idio pathic PD, addressing concrete and abstract concepts, conceptual attributes , and conceptual relations. Methods: Twelve patients with preserved cognitive status, 12 patients with mildly deteriorated cognitive status, and 12 control subjects were studied. The cognitive status of patients and controls was determined using detaile d cognitive testing. Patients were participants in a university-based movem ent disorder program, and their PD diagnoses were clinically confirmed duri ng longterm follow-up. The 2 patient groups were similar in age, level of e ducation, disease duration, and parkinsonian disability. Patients were requ ired to produce verbal descriptions of concrete and abstract concepts, to g ive ratings of the importance of concept attributes, and to assess and cons truct conceptual hierarchies. The description tasks included guiding questi ons, which were used if the spontaneous productions of the patients lacked any essentials expected in the answers. Results: Patients with mild cognitive deterioration performed less well tha n the other groups in defining concrete and abstract concepts (P<.001 for b oth). External guidance did not help them markedly improve their performanc e. They also had difficulties in tasks calling for knowledge of the importa nce of given attributes to the concepts and in tasks demanding evaluation o f hierarchical semantic relations between concepts (P<.001 for both). Conclusion: Semantic disruption is implied in idiopathic PD in association with incipient cognitive impairment.