A clinically valuable method is provided for evaluating the onset or progression of Alzheimer's disease using a non-invasive biomarker obtained from an independent component analysis (ICA) of an individual's resting state functional MRI. The method is relatively more automated and objective than previous methods and exploits dysfunctional connectivity across an entire network of brain regions in Alzheimer's disease. It eliminates the need for investigator's intervention as much as possible and is more robust than structural and functional methods targeting the hippocampus.