Neuronal microscale biophysical instability mediates macroscale network dynamics shaping pathological manifestations

Microscale biophysical alterations in neuronal dynamics can have profound implications for macroscale pathological outcomes in the brain. Despite the critical need to link neuronal perturbations to large-scale disease manifestations, few studies successfully bridge these hierarchical scales. Here, we bridge microscale biophysical variability within neuronal dynamics to macroscale disease-related phenotypes. We find that <i>Drosophila</i> models expressing tauopathy- and epilepsy-associated molecular mutations exhibit increased dynamic instability in the timing of action potential initiation, and microscale biophysical changes are manifested at the level of the macroscale global brain state. We show that variability in voltage-gated sodium channel currents during non-stationary channel inactivation may act as a microscale biophysical contributor to the increased dynamic instability observed in action potential timing. We also find that treatment with antiepileptic drugs stabilizes neuronal dynamics by modulating this variability in voltage-gated sodium channel currents. Finally, we show that neurons derived from human induced pluripotent stem cells (iPSCs) from patients with Alzheimer's disease and epilepsy exhibit analogous dynamic instability, which is reversible by administration of antiepileptic medications. Our results highlight how subtle microscale neuronal instabilities propagate and are amplified to produce macroscopic pathological phenotypes, providing new biophysical insights into neurological disorders and potential strategies for therapeutic intervention.