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In this issue of the journal, Lerman et al1 report on a new composite measurement, the resource allocation index (RAI), which represents the relative strength of interactions during the resting state between the 3 major brain networks: the “default mode” network (DMN), the “executive control” network (ECN), and the “salience” network (SN). This work benefits from the recent extension of functional connectivity assessment with functional magnetic resonance imaging to studies of large-scale networks and their interaction to provide systems-based evaluations of the nervous system.2 As the authors note, separate brain networks are thought to subserve task-relevant vs task-independent (eg, internally focused) cognitive processing. The ECN is implicated in cognitive control and goal-directed attention,3 and the DMN shows reduced activity during cognitive tasks and reflects self-referential and episodic memory processing.4 The SN facilitates orientation to external vs internal information.5 Using the RAI, Lerman et al1 illustrate a fundamental role of the SN in toggling resource allocation between the ECN and the DMN during the different states of brain function associated with smoking abstinence and smoking satiety in heavy smokers. They also show a negative association of the RAI with abstinence-induced craving for smoking and a positive association of the RAI with DMN activity suppression during subsequent performance of a working memory task.
London ED, Ghahremani DG. Large-Scale Brain Network Coupling as a Potential Neural Metric for Nicotine Abstinence Effects on Craving and Cognitive Function. JAMA Psychiatry. 2014;71(5):491-492. doi:10.1001/jamapsychiatry.2013.4109