While electroencephalography (EEG) was mainly used to study babies and young children, magnetic resonance imaging (MRI) and functional MRI (fMRI) are widely used for brain research because of its high resolution, multiple advances in image analyses, and the large range of image contrasts that they provide. Structural MRI provides information on brain morphometry, such as cortical thickness or area, and cortical and subcortical volumes. Using specific stimulation paradigms, functional MRI (fMRI) can yield information on functional networks dedicated to a particular task and their connectivity. Similarly, resting-fMRI (rs-fMRI) or task-free fMRI can provide an estimate for the functional connectivity in the brain at rest (without an activation paradigm). These task-free brain activities appear to reflect coordinated and intrinsic spontaneous fluctuations in brain activity at baseline (Gusnard and Raichle 2001). Rs-fMRI provides insight into the unprompted activity that is naturally produced within the brain, which subsequently promotes communication across regions.
