Effects of aging on default mode network activity in resting state fMRI: does the method of analysis matter?
1Institute for Clinical Radiology, Department of Psychiatry & Alzheimer Memorial Center, University of Munich, Marchioninistr. 15, 81377 Munich, Germany. walter.koch@med.uni-muenchen.de
Unlabelled:
Functional MRI (fMRI) of default mode network (DMN) brain activity during resting state is gaining attention as a potential non-invasive biomarker to diagnose incipient Alzheimer's disease. The aim of this study was to identify effects of normal aging on the DMN using different methods of fMRI processing and evaluation.
Methods:
fMRI was acquired in 17 young and 21 old healthy subjects and the data were analyzed with (a) volumes of interest (VOI)-based signal time course and (b) independent component analyses (ICA). In the first approach, the strength of DMN region inter-connectivity (as expressed with correlation coefficients) was of primary interest, the second method provided a measure of the magnitude of DMN co-activation.
Results:
The older subjects exhibited significantly lower DMN activity in the posterior cingulate (PCC, t-test P<.001) as well as a tendency to lower activity in all other DMN regions in comparison to the younger subjects. We found no significant effect of age on DMN inter-connectivity.
Conclusion:
Effects of normal aging such as loss of PCC co-activity could be detected by ICA, but not by signal time course correlation analyses of DMN inter-connectivity. This either indicates lower sensitivity of inter-connectivity measures to detect subtle DMN changes or indicate that ICA and time course analyses determine different properties of DMN co-activation. Our results, therefore, provide fundamental knowledge for a potential future use of functional MRI as biomarker for neurodegenerative dementias where diminished DMN activity needs to be reliably differentiated from that observed in health aging.
Insights
Normal aging reduces default mode network (DMN) activity, particularly in the posterior cingulate cortex. Independent component analysis (ICA) detected these changes, unlike traditional correlation methods, offering insights for Alzheimer's disease biomarker development.
Area of Science:
- Neuroimaging
- Neuroscience
- Gerontology
Background:
- Functional MRI (fMRI) of the default mode network (DMN) is a potential biomarker for early Alzheimer's disease.
- Understanding normal aging effects on the DMN is crucial for differentiating disease from healthy changes.
Purpose of the Study:
- To investigate the impact of normal aging on DMN activity.
- To compare different fMRI processing methods for detecting age-related DMN changes.
Main Methods:
- fMRI data acquired from 17 young and 21 older healthy adults.
- Analysis using (a) volume of interest (VOI)-based time course correlation and (b) independent component analysis (ICA).
Main Results:
- Older adults showed significantly lower DMN activity in the posterior cingulate cortex (PCC) and a trend for lower activity in other DMN regions.
- No significant age-related differences were found in DMN inter-connectivity using correlation analysis.
Conclusions:
- ICA effectively detected age-related decreases in DMN co-activity, while correlation analyses did not.
- Findings highlight ICA's potential for detecting subtle DMN alterations and its importance in developing biomarkers for neurodegenerative diseases.
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