What is the Origin of Default Mode Network?

The DMN was first identified and characterized through functional magnetic resonance imaging (fMRI) studies in the early 2000s, observed as a consistent pattern of brain activity that was default or present when the brain was "at rest." Its relevance in the hormonal domain stems from the neuroendocrine system's profound influence on cognitive and affective states, linking brain activity to systemic hormone release. This discovery provided a neural correlate for self-referential thought and its physiological impact.

What is the Mechanism of Default Mode Network?

The DMN is primarily comprised of the medial prefrontal cortex, posterior cingulate cortex, and inferior parietal lobule. Its activity is inversely correlated with attention-demanding tasks, suggesting a switch between internal and external focus. Chronic stress and hormonal imbalances, particularly elevated cortisol, can alter the functional connectivity within the DMN, potentially leading to a sustained state of internal preoccupation and anxiety, which further perpetuates HPA axis dysregulation through a neuro-hormonal feedback loop.

Default Mode Network

Meaning

The Default Mode Network (DMN) is a large-scale brain network of interconnected regions that shows increased activity when an individual is not focused on the external world, such as during introspection, planning, or mind-wandering. In hormonal health, the DMN’s activity and connectivity are relevant because they are intimately linked to stress perception, emotional regulation, and the chronic stress response mediated by the HPA axis. Dysregulation of the DMN can correlate with chronic anxiety and altered neuroendocrine signaling.