Abstract / Summary
For more than 150 years, since the idea that mental illness is rooted in the brain first emerged in the mid-1800s, psychiatry has searched for a reliable biological system to anchor its understanding of mental illness. This paper proposes a candidate for that system, starting from a striking observation. Almost every major psychiatric disorder shows three things together: REM sleep disturbance, altered default mode network (DMN) activity, and emotional dysregulation. The DMN is independently known to play a central role in emotional regulation and emotional memory, which is what suggests these three recurring findings are not coincidental but are manifestations of a single, previously unidentified biological system. The Somnogenesis System hypothesis states that the DMN's three principal hubs, the medial prefrontal cortex, the posterior cingulate cortex and precuneus, and the bilateral inferior parietal cortices, reactivate in a specific, ordered sequence during every REM period, and that this order is identical across the large majority of healthy individuals. Each hub carries an established, distinct function, and the evidence suggests these functions operate as a dependency chain rather than as independent, parallel contributions, consistent with the proposed existence of a genuine biological system rather than three regions coincidentally active at the same time. This hypothesis can be tested without collecting new data. A protocol is proposed using an existing public dataset of simultaneous EEG-fMRI sleep recordings, in which the three hubs are anatomically defined using a standardized cortical atlas and each REM period's activation order is estimated from onset latency rather than raw BOLD timing, controlling for each region's own hemodynamic response. Confirming the hypothesis would reframe REM sleep as the physiological interface of an underlying biological system, with implications for conditions including Parkinson's disease, dementia with Lewy bodies, multiple system atrophy, and major depressive disorder, where a disrupted system rather than a disrupted stage may be the more precise marker of pathology. The hypothesis is directly falsifiable, a failure to find a consistent, shared order would refute it outright.