Enhanced setup for wired continuous long-term EEG monitoring in juvenile and adult rats: application for epilepsy and other disorders.

BACKGROUND: The electroencephalogram (EEG) is a widely used laboratory technique in rodent models of epilepsy, traumatic brain injury (TBI), and other neurological diseases accompanied by seizures. Obtaining prolonged continuous EEG tracings over weeks to months is essential to adequately answer research questions related to the chronobiology of seizure emergence, and to the effect of potential novel treatment strategies. Current EEG recording methods include wired and the more recent but very costly wireless technologies. Wired continuous long-term EEG in rodents remains the mainstay approach but is often technically challenging due to the notorious frequent EEG cable disconnections from the rodent's head, and to poor signal-to-noise ratio especially when simultaneously monitoring multiple animals. Premature EEG cable disconnections and cable movement-related artifacts result from the animal's natural mobility, and subsequent tension on the EEG wires, as well as from potential vigorous and frequent seizures. These challenges are often accompanied by injuries to the scalp, and result in early terminations of costly experiments. RESULTS: Here we describe an enhanced customized swivel-balance EEG-cage system that allows tension-free rat mobility. The cage setup markedly improves the safety and longevity of current existing wired continuous long-term EEG. Prevention of EEG cable detachments is further enhanced by a special attention to surgical electrode anchoring to the skull. In addition to mechanically preventing premature disconnections, the detailed stepwise approach to the electrical shielding, wiring and grounding required for artifact-free high signal-to-noise ratio recordings is also included. The successful application of our EEG cage system in various rat models of brain insults and epilepsy is described with illustrative high quality tracings of seizures and electrographic patterns obtained during continuous and simultaneous monitoring of multiple rats early and up to 3 months post-brain insult. CONCLUSION: Our simple-to-implement key modifications to the EEG cage setup allow the safe acquisition of substantial high quality wired EEG data without resorting to the still costly wireless technologies.

Methods in Electrode Implantation and Wiring for Long-Term Continuous EEG Monitoring in Rodent Models of Epilepsy and Behavioral Disturbances.

Rodent seizure models that pathologically and behaviorally recapitulate age-tailored epileptic disorders are used by us and others to advance our understanding of the chronobiology and mechanisms of epileptic seizure emergence and their comorbidities and to investigate potential novel treatment strategies. Obtaining prolonged continuous electroencephalogram (EEG) tracings over months is essential in this line of translational research, particularly to assess the relation between electrographic changes and the development of seizures and their various psychiatric and cognitive comorbidities in models where seizures gradually emerge over weeks following brain insults. Here we describe our approach to electrode implantation and wiring in order to successfully obtain high-quality continuous EEG tracings in rats for prolonged periods. A detailed stepwise methodological description is provided with a special focus on the details that help most in avoiding notorious pitfalls such as premature EEG cable disconnections and a poor signal to noise ratio.