Figure 1.

Interactions among the default mode, salience and executive control networks, and shift to an alerted default mode for adaptive responses to environmental changes and stressors. (A) Dynamic functional connectivity patterns are tightly linked to adaptive behavior as a guide toward optimal behavioral performance²⁴. The DMN is most active during the resting state, with deactivation occurring during task performance²². Dynamic interactions among DMN, ECN and SN play an important role in the shift between resting and focused attention. The ECN and/or SN may negatively regulate activity in the DMN. The ECN and SN exert control over the DMN⁴⁰ and may play a preferential role in trial-to-trial adaptive control; such adaptation may involve balancing internally-oriented DMN activity and externally-oriented task-related ECN/SN activity. The DMN global network topology is dynamically linked to brain state and it dramatically changes over the 24-hour day during different brain states⁴⁵. (B) Stress increases connectivity of DMN, shifting towards an alerted default mode⁴⁴. Acute stress responses upregulate the SN. Altered connectivity within the SN is paralleled by changes in the ECN. Prolonged stress leads to DMN hyperactivity⁴⁷; the DMN is intrinsically related to both SN and ECN. Microgravity may also induce changes in resting-state functional connectivity of the DMN.