ELECTROPHYSIOLOGICAL SIGNATURES IN ACUTE SLICES OF LIVING HUMAN EPILEPTOGENIC CORTEX AND HIPPOCAMPUS

Elucidating the cellular mechanisms of human epileptogenesis requires direct investigation of pathological network dynamics in ex vivo tissue. Acute brain slices derived from resected human cortex offer a critical experimental platform to assess intrinsic neuronal properties and aberrant circuit behavior within a disease-relevant context. In this study, we characterized surgically resected cortical tissue from patients with focal drug-resistant epilepsy (Kyyriäinen et al., 2025), utilizing a multimodal approach that includes whole-cell patch-clamp recordings and extracellular microelectrode array (MEA) electrophysiology. We systematically evaluated the efficacy of two established in vitro induction paradigms — high K⁺/low Mg²⁺ solution and 100 µM 4-aminopyridine (4-AP) — in generating epileptiform activity. While these protocols are ubiquitous in rodent studies, their specific impact on human epileptogenic cortex and hippocampus activity remains underdefined, particularly given the distinct intrinsic properties and reorganized synaptic circuitry inherent to human pathology. Our data reveal significantly divergent network responses. The high K⁺/low Mg²⁺ model induced a robust depolarizing shift in resting membrane potential, consistently driving human neurons into sustained, synchronized firing patterns characteristic of ictal-like events. Conversely, 4-AP administration failed to produce comparable tonic depolarization, instead eliciting intermittent burst firing and interictal-like discharges without sustained transitions. These findings demonstrate that global ionic manipulation instigates a hyper-excitable state more closely resembling seizure activity in human tissue than potassium-channel blockade alone. Collectively, this work provides essential insights into the translational validity of classical in vitro models for human epileptogenic tissue, enabling the selection of appropriate models for future translational epilepsy research.