Basal forebrain metabolism in Alzheimer's disease continuum: relationship with education

Abstract

We analyzed education, as a proxy of cognitive reserve, and the cholinergic pathway in Alzheimer's disease (AD), to test the hypothesis that education might modulate the relationship between clinical symptoms and metabolic and structural changes in AD. We included 84 subjects and compared between diagnostic groups and different educational levels the glucose metabolism of basal forebrain (BFM) and volume of the basal forebrain, the major cholinergic structure, and hippocampus (HM) (and hippocampal volume), a relevant projection site for the basal forebrain. Correlations with the global cognitive status and education in the whole sample were also performed. Patients with AD dementia showed reduced basal forebrain volume, hippocampal volume, and HM compared with controls. In the whole group, the global cognitive status was positively correlated with BFM and HM. Among high-educated subjects, mild cognitive impairment showed higher BFM and HM in comparison to other diagnostic groups. Our results suggest that in mild cognitive impairment subjects with a higher educational level, cholinergic activity is upregulated and this appears to have a compensatory effect, which may be lost in later symptomatic stages.

Keywords: Alzheimer's disease (AD); Basal forebrain; Education; Fluorodeoxyglucose (FDG); Positron emission tomography (PET); Reserve.