Dynamic brain network reconfiguration under stress: A multiphase fMRI study

Acute stress induces a dynamic reallocation of neural resources across three distinct phases: Pre-stress, Stress, and Post-stress. Despite extensive research on isolated phases, a critical gap remains in understanding how this resource reconfiguration shapes the brain's dynamic characteristics across the entire temporal continuum. To address this gap, we employed Hidden Markov Modeling (HMM) to investigate whole-brain network dynamics continuously across all phases in two independent cohorts using the ScanSTRESS (n = 77, 35 females) and Montreal Imaging Stress Task (n = 48, 24 females). Our results revealed rapid and reversible spatiotemporal reconfigurations of large-scale brain networks, accompanied by elevated cortisol levels in both cohorts. Specifically, a marked spatiotemporal reconfiguration of brain networks was observed from Pre-stress to Stress phases, characterized by overall suppressed activation of the executive control network, alongside enhanced sensory processing, and increased functional coupling among salience, sensory, and executive networks. These changes reversed during the Post-stress phase, with no significant differences between Pre- and Post-stress phases. Critically, we identified robust individual differences: females exhibited higher state switching rates during stress across both cohorts, and a poorer post-stress recovery index (greater deviation from baseline) was associated with higher depression and anxiety scores. Synthesizing these findings, we propose a Tri-Phase Network Reconfiguration Model positing that allostasis is achieved through phase-specific brain state repertoires and directed transitions. This dynamic framework advances our understanding of stress adaptation and offers testable hypotheses for how these processes may be dysregulated in stress-related psychopathology.