A Cost-Effective and Minimally Invasive Protocol for Chronic Multi-Site Electroencephalography Recording in Freely Moving Mice.

Electroencephalography (EEG) serves as a fundamental tool for tracking electrical activity in the brain and has become increasingly important in both clinical diagnostics and preclinical animal research. While rodent EEG offers a powerful platform for modeling human neurological disorders, long-term recordings are often limited by the high cost, invasiveness, or technical complexity of existing systems. Here, we present a reliable, accessible, economically viable, and minimally intrusive protocol for chronic, multi-site cortical EEG acquisition in freely moving mice. The technique involves fabricating platinum-iridium wires with screw electrodes connected to a universal serial bus (USB)-type interface, which are anchored epidurally using bone screws and secured with adhesive and dental cement. The system allows for stable signal capture over several months, as demonstrated in wild-type C57BL/6J mice with an 85% post-operative survival rate (n = 20). EEG was sampled at 1,000 Hz and filtered between 1 Hz and 500 Hz using a differential amplifier setup. To validate the system, pentylenetetrazol (20 mg/kg) was administered to induce seizure-like activity, leading to a marked increase in interictal discharges-from 2-5 at baseline to 20-51 events post-injection-accompanied by increased signal amplitude. Discharges were identified based on waveform morphology and signal characteristics matching recognized electrophysiological criteria. The setup is compatible with behavioral video tracking and open-source analysis pipelines, and supports integration with pharmacological, genetic, or neuromodulation studies. This method provides a stable and adaptable platform for investigating brain network dynamics in rodent models, with applications in epilepsy research and beyond.