Data from 848 adults of all ages has found that brain volume in the default mode network declined in both healthy and pathological aging, but the greatest decline occurred in Alzheimer’s patients and in those who progressed from mild cognitive impairment to Alzheimer’s disease. Reduced brain volumes in these regions were associated with declines in cognitive ability, the presence of Alzheimer’s biomarkers in the cerebrospinal fluid, and with carrying the “Alzheimer’s gene”, the APOE4 allele.
The findings support the idea that neurodegeneration spreads through networks of connected brain regions, in a disease specific manner.
 . Structural Covariance of the Default Network in Healthy and Pathological Aging. The Journal of Neuroscience [Internet]. 2013 ;33(38):15226 - 15234. Available from: http://www.jneurosci.org/content/33/38/15226