Review of resting-state functional connectivity methods and application in clinical populations

Functional magnetic resonance imaging (fMRI) studies of the resting state have provided consistent and reliable brain networks defined by spatially distinct regions whose interactions are both functionally segregated and integrated across the whole brain. Functional connections integrate multiple brain systems to produce unique networks attending to the different cognitive and sensory demands of the body. Detection and quantification of functional connectivity has been fundamental to the investigation of behavioral and clinical abnormalities in brain function using noninvasive human neuroimaging. It has expanded our ability to examine the brain physiology and pathophysiology across different age groups and clinical populations. Several techniques exist in literature to identify and quantify the functional connectivity metrics of brain regions using resting-state fMRI. In this chapter, we review the neurophysiological basis of resting-state functional connectivity and give a synopsis of the most established resting-state analysis techniques. We also summarize relevant findings from an array of clinical populations including neuropsychological disorders to emphasize the versatility of resting-state fMRI.