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The relationship between fMRI activation and cerebral atrophy: comparison of normal aging and alzheimer disease
S C Johnson1, A J Saykin, L C Baxter
1Department of Psychiatry, New Hampshire Hospital, Lebanon, New Hampshire, 03756, USA.
Abstract:
Functional MRI has recently been used to examine activation associated with aging and dementia, yet little is known regarding the effect of cerebral atrophy on fMRI signal. The purpose of this study was to examine the relationship between measures of global and regionally specific atrophy and fMRI activation in normal aging and in Alzheimer disease (AD). Two groups of subjects were studied with echoplanar imaging and quantitative structural volumetry: healthy controls spanning a broad age and atrophy range (n = 16) and patients with mild AD (n = 8). Results from a semantic task previously found to activate left inferior frontal (LIFG) and left superior temporal (LSTG) gyri were analyzed. The correlations between clusters of activation in the LIFG and LSTG and measures of local atrophy in the LIFG and LSTG regions were evaluated. For control subjects, there was no significant correlation 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 significant 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 activation of language regions and atrophy within those regions may be independent among healthy adults spanning a broad age and atrophy range. However, in AD, a relationship exists in the LIFG that may reflect compensatory recruitment of cortical units or disease-specific changes in the hemodynamic response.
Insights
In healthy adults, brain atrophy does not affect functional MRI (fMRI) language activation. However, in Alzheimer disease (AD), increased atrophy in the left inferior frontal gyrus correlates with higher fMRI activation, suggesting compensatory mechanisms.
Area of Science:
- Neuroimaging
- Cognitive Neuroscience
- Aging Research
Background:
- Functional MRI (fMRI) is used to study aging and dementia, but the impact of cerebral atrophy on fMRI signals is not well understood.
- Investigating the relationship between brain atrophy and brain activity is crucial for understanding cognitive decline.
Purpose of the Study:
- To examine the relationship between global and regional cerebral atrophy and fMRI activation in healthy aging and Alzheimer disease (AD).
Main Methods:
- Studied two groups: healthy controls (n=16) and mild AD patients (n=8) using echoplanar imaging and quantitative structural volumetry.
- Analyzed fMRI activation during a semantic task focusing on the left inferior frontal gyrus (LIFG) and left superior temporal gyrus (LSTG).
- Correlated activation clusters in LIFG and LSTG with local atrophy measures in these regions.
Main Results:
- In healthy controls, no significant correlation was found between brain atrophy and fMRI activation in LIFG (r = -0.03) or LSTG (r = 0.20).
- In AD patients, a significant positive correlation was observed between atrophy and activation in LIFG (r = 0.70, P = 0.05), but not in LSTG (r = 0.00).
Conclusions:
- Brain activation in language regions and atrophy within these regions appear independent in healthy adults across a wide age and atrophy range.
- In AD, a relationship between LIFG atrophy and activation suggests potential compensatory recruitment or disease-specific hemodynamic changes.