Disorders in intentional gestural organization in Alzheimer's disease: combined or selective impairment of the conceptual and production systems?

This study examines disorders which affect the intentional gestural organization in Alzheimer's disease. An original and prospective protocol which assessed both the conceptual and production systems (with reference to the Roy and Square model 1985) was presented to 16 patients with Alzheimer's disease (mild to moderate dementia) and 40 healthy elderly subjects. Our study showed impairment of both systems in the Alzheimer's patients group. Two patients presented reverse performance profiles, which were characterized in one case by preservation of the conceptual system and impairment of the production system and in the other by the reverse dissociation. The findings demonstrated that disorders in the intentional gestural organization in Alzheimer's disease usually affect both the conceptual and production systems. The hypothesis concerning the existence of two functionally distinct systems underlying the organization of intentional body movement was corroborated (1) by a lack of significant correlation between the scores obtained in the assessment of the two systems and (2) by the demonstration of the double dissociation.