Quantifying the collapse of the ventral CA1 excitability margin links emotional memory replay with environmental synchronisation in schizophrenia, depression, and PTSD

We introduce the Excitability-Margin Model (EMM), a unifying quantitative framework in which narrowing of the ventral CA1 excitability buffer (ΔVmargin) below ≈ 5 mV allows ordinary hippocampal oscillations (θ, ripple, dendritic plateaus, extracellular K⁺ bursts) to trigger involuntary replay of emotional engrams. A meta-analysis of chronic restraint stress (CRS) recordings reveals four convergent processes — KCC2 down-regulation, NKCC1 up-regulation, loss of GIRK/TASK leak currents, and reduced Na⁺/K⁺-ATPase α1 — that depolarise vCA1 by 11.3 ± 1.5 mV. Additional excitability-narrowing influences include genetic variants (CACNA1C rs1006737 A, SCN2A R1882Q gain-of-function), psychoactive substances (THC, ethanol, nicotine, chronic caffeine), systemic inflammation (viral interleukin-6, cytokine cascades), metabolic shifts (high-sugar diets, insulin resistance), oxidative stress (ROS generation, glutathione depletion), and emerging toxicants such as microplastic-derived contaminants and particulate matter (PM2.5, PM10). Together these risk factors collapse the safety margin to ≤ 5 mV, rendering common network events pathogenic.Once the buffer is breached, the valence of the re-activated engram determines disease trajectory. Fear-biased replays drive dopamine release and sustained cortisol elevation, shifting the glutamate/GABA ratio toward excitation and locking vCA1 into a depolarised state. Repeated activations generate reactive oxygen species, deplete glutathione, and trigger progressive loss of parvalbumin interneurons (PV-INs). The weakening of perisomatic inhibition amplifies excitatory drive, narrows ΔVmargin even further, and permits an expanding range of otherwise benign transients to trigger unwanted engrams — accelerating the shift in excitatory/inhibitory balance and progression toward the schizophrenia phenotype. Sadness-biased loops engage CRF and HPA-axis dysregulation leading to major depressive disorder, while trauma-biased replays recruit noradrenaline bursts evolving toward PTSD. Persistent vCA1 hyperexcitability thus links chronic stress, genetic susceptibility, inflammatory states, metabolic dysfunction, environmental toxicants, and psychoactive exposures into a convergent mechanism of disease.The model also predicts that 7–30 Hz extremely-low-frequency (ELF) magnetic fields, transduced by biogenic magnetite chains, can phase-bias the hippocampal θ-oscillator and increase co-activation probability. Observational studies report associations between geomagnetic storms (Kp ≥ 6) and acute surges in psychiatric hospitalisations, suicide attempts, and cardiovascular events; within EMM, these correlations are interpreted as transient synchronisation and amplification effects in narrow-margin neurons.Long-term remission is expected to require widening ΔVmargin to ≥ 7 mV, with ≈ 9 mV providing robustness against common transients. We outline a Four-Axis Reset (FAR) framework: (i) hyperpolarisation of Vrest, (ii) chloride reset, (iii) PV/KCC2 restoration with ROS reduction, and (iv) narrowing of the γ/θ integration window. Falsifiable, non-invasive operational markers include reduction of on-scalp MEG γ-bursts (≥ 35 %, p < 0.05) and increased heart-rate-variability rMSSD (≥ +5 ms, p < 0.05); exploratory endpoints include ²³Na-MRI (ionic reserve, directional) and PET-KCC2 if tracers become available. Achieving these endpoints in preregistered IRB-approved pilot studies would provide the first in-vivo validation of EMM and authorise progression to RCT II.