The relationship between fMRI activation and cerebral atrophy: Comparison of normal aging and Alzheimer disease

Functional MRI has recently been used to examine activation associated with aging and dementia, yet little is known regarding the effect of cerebral a trophy on fMRI signal. The purpose of this study was to examine the relatio nship between measures of global and regionally specific atrophy and fMRI a ctivation in normal aging and in Alzheimer disease (AD). Two groups of subj ects were studied with echoplanar imaging and quantitative structural volum etry: healthy controls spanning a broad age and atrophy range (n = 16) and patients with mild AD (n = 8), Results from a semantic task previously foun d to activate left inferior frontal (LIFG) and left, superior temporal (LST G) gyri were analyzed. The correlations between clusters of activation in t he LIFG and LSTG; and measures of local atrophy in the LIFG and LSTG; regio ns were evaluated. For control subjects, there was no significant correlati on between activation and regional or total brain atrophy (for LIFG r = -0. 03, NS; for LSTG r = 0.20, NS). In contrast, for AD patients, there was a s ignificant positive correlation between atrophy and activation in LIFG (r = 0.70, P = 0.05) but not LSTG (r = 0.00, NS). These results suggest that ac tivation of language regions and atrophy within those regions may be indepe ndent among healthy adults spanning a broad age and atrophy range. However, in AD, a relationship exists in the LIFG that may reflect compensatory rec ruitment of cortical units or disease-specific changes in the hemodynamic r esponse. (C) 2000 Academic Press.