Resting state fMRI ( rs-fMRI or R-fMRI ) is a method of functional
magnetic resonance imaging (fMRI) that is used in brain mapping to evaluate
regional interactions that occur in a resting or task-negative state, when an
explicit task is not being performed. A number of resting-state brain networks
have been identified, one of which is the default mode network. These brain
networks are observed through changes in blood flow in the brain which creates
what is referred to as a blood-oxygen-level dependent (BOLD) signal that can
be measured using fMRI.
Because brain activity is intrinsic, present even in the absence of an
externally prompted task, any brain region will have spontaneous fluctuations
in BOLD signal.