The default mode network (DMN) is linked to self-referential thinking, memory, and goal-directed cognition. Its functional connectivity with frontoparietal networks involved in attention and executive control may indicate cognitive health. This review examines DMN connectivity metrics as potential biomarkers across states like attention, mind wandering, and meditation, and in conditions such as Alzheimer's disease, Parkinson's disease, depression, and ADHD. It also addresses the reliability of network estimation and offers recommendations for using functional connectivity measures as biomarkers of cognitive health.
Ketamine treatment alters how brain networks dynamically interact in people with treatment-resistant depression. After four ketamine infusions over two weeks, patients spent less time in a visual-network brain state and more time in a central-executive-network state. Transitions between the salience network and central executive network increased, while salience-to-visual transitions decreased. Reduced time in the salience-network state was linked to less rumination. Before treatment, depressed patients differed from healthy controls in these same dynamic patterns, suggesting ketamine may shift network dynamics toward a healthier profile.