Functional connectivity arises from a slow rhythmic mechanism

Functional connectivity MRI has revolutionized our understanding of brain architecture. Correlated changes in oxygen levels reveal networks of regions. These networks, each linked to particular functions, are conserved across individuals and species. Normal development, learning, and mental disorders are associated with subtle network changes, providing insight into how brains work. Remarkably, the basis of functional connectivity remains unknown. Although some studies have reported data consistent with an oscillatory process, the leading hypothesis involves emergent, arrhythmic dynamics of complex and distributed networks (the “criticality” hypothesis). By using a new electrode-based technique, we show that functional connectivity is not related to criticality, but instead to specific and potentially localizable oscillatory processes. This finding provides a tool to identify the mechanisms underlying functional connectivity.