Dementia and the default mode.

Changes in regional activity levels and network connectivity occur across the lifespan within the default mode network (DMN) of resting brain function. Changes with age are noted in most components of the DMN, especially in medial frontal/anterior cingulate and posterior cingulate/precuneus regions. Individuals with age-related disease such as mild cognitive impairment (MCI) and Alzheimer's disease (AD) demonstrate additional default-related changes particularly in posterior cingulate/precuneus and hippocampal regions. As these regions are areas of known pathologic change in both normal aging and age-related disease, examining DMN activity may allow future studies to more fully assess the relationship between pathology and function in these regions. The ability to form this structure-function link could allow us to determine critical factors involved in the decline or preservation of function in the presence of age-related neuropathology.