The Relationships between Executive Dysfunction and Frontal Hypometabolism in Alzheimer’s Disease.

Abstract. A series of tasks assessing executive functions was administered to patients with Alzheimer’s disease and control subjects. Two groups of Alzheimer patients were examined: patients with hypometabolism restricted to the posterior (temporal and parietal) cerebral areas and patients with hypometabolism in both posterior and anterior (frontal) cerebral areas. The performance of the Alzheimer patients was inferior to control subjects on all executive tasks. However, the two groups of Alzheimer patients did not differ from each other on all tasks except one. These data indicate that frontal lobe hypometabolism is not necessary to produce executive impairment in Alzheimer’s disease. Consequently, executive dysfunction could be the consequence of a disconnection process between posterior and anterior cerebral areas. Introduction. The presence of executive dysfunction relatively early in Alzheimer’s disease is now well established (e.g. Collette et al., 1999a). However, there exists at present some debate concerning the neurobiological substrates of these deficits. Indeed, for some authors, executive impairment is specifically related to frontal lobe impairment (e.g. Shallice, 1988) but frontal lobe dysfunction does not seem to be a prominent feature in the earlier stages o