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

Abstract

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.

Modelling epilepsy in the mouse: challenges and solutions

“…However, rats with clinically relevant mutations have also been studied ( Ohmori et al, 2020 ). Diverse EEG setups have been developed for both tethered ( Medlej et al, 2019 ) and wireless ( McGuire et al, 2019 ) EEG in rats, and ex vivo brain slice preparations can be used to study seizure susceptibility ( Accardi et al, 2018 ) and epileptogenesis ( Dyhrfjeld-Johnsen et al, 2010 ), and to screen ASDs ( Hill et al, 2010 ).…”

Research on mechanism of the effect of charred hawthorn on digestive by SCF /c-kit pathway

“…Olfactory bulb is the physiological basis of odor administration, and hypothalamus is the integrated center of energy balance and regulation of gastrointestinal function. Since EEG is an intuitive re ection of electrical activity, excitation or inhibition in brain regions, we further investigated the effects of OCHT on that of these regions using EEG [30,31] . Raw hawthorn and charred hawthorn can signi cantly increase the amplitude of isolated gastrointestinal smooth muscle in rats.…”

OSERR: an open-source standalone electrophysiology recording system for rodents

“…Periodograms were calculated for each epoch using a Hamming window and averaged to obtain the final PSD estimate at a 0.5 Hz spectral resolution. The PSD was integrated using the trapezoidal method to find the power in individual bands: delta (1-4 Hz), theta (4-8 Hz), alpha (8-13 Hz), beta (13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30), and gamma (30-100 Hz). The gamma band was further divided into low gamma (30-60 Hz) and high gamma (60-100 Hz).…”

“…Depending on the requirements of the experiment, the advantages and disadvantages of different recording systems need to be carefully considered. As mentioned earlier, tethered systems can record from a large number of channels with high sampling frequencies, suitable for recording neuronal ensembles or high-resolution activity mapping in both global and local brain areas [23][24][25] . Telemetry systems offer the versatility of being wireless and restraint-free, and are less prone to induce injuries in the subjects [26][27][28][29][30] .…”

“…While offering important advantages such as high channel count up to many thousands 23 , 24 , tethered systems limit the movement of the subjects, and may affect behavioral phenotype. In addition, other potential problems are also associated with tethered systems, including susceptibility to electromagnetic interference and movement artifacts, as well as the risk that tethered animals may injure themselves or disrupt the recording by pulling on the cable 25 . Radio telemetry systems allow test subjects to move freely 26 – 32 , and both tethered and telemetry systems offer the advantage of real-time data streaming for visualization and closed-loop headstage communication.…”