Implanting an On-Head Electrode System in a Rat Model for Real-Time Seizure Detection

Take an anesthetized rat with the exposed, cleaned temporal bones situated bilaterally to the intracortical neurons-rich parietal cortex.

Place a stimulation electrode filled with an electroconductive gel on one temporal bone for electrical contact and secure it with dental cement.

Fix another stimulation electrode on the opposite temporal bone for uniform stimulation of the parietal region.

Drill holes in the skull and insert anchor screws to stabilize the implant.

Place the recording electrodes in the parietal cortex to capture signals from the intracortical neurons which are involved in the development of seizures, the abnormal electrical activity.

Secure the screws and electrodes with dental cement.

Connect the electrode wires to a head-mounted amplifier and attach a mesh protector around it to protect the amplifier and the electrodes.

Wash the exposed tissues with disinfectant, inject local anesthesia, and suture the wound.

The rat with the implanted on-head electrode system is ready for real-time seizure detection.

In this procedure, remove most of the hair from the animal's scalp with a hair clipper. Next, apply depilatory cream on the scalp, spread it evenly on the surface, and wait a few minutes. Use a spatula to gently remove the cream, and the remaining hair. Rinse the skin with disinfectant. Inject 1% to 2% lidocaine subcutaneously to numb the skin. Then, apply a single drop of vet ointment on each eye. Make a thorough and long sagittal incision along the midline with the scalpel, from the forehead to the neck.

Subsequently, dissect the tissues, including the periosteum from the skull. Then, using a chisel or tooth tweezers, clean the area between the cristae of the two temporal bones. Keep the skull exposed by retracting the dissected skin using four bulldogs.

Gently, place the fine tweezers between the steep edge of the temporal bone and the muscles, and separate them. Make jiggling movements to expose as much of the large surface of the temporal bone as possible, preferably from the edge of the occipital bone to the plane of the coronal sutures, without damaging the muscles. Following that, place the retractors bi-temporally to keep the temporal bones exposed.

Rinse the surface of the skull with one to two milliliters of 3% hydrogen peroxide. Then, wash it with one to two milliliters of water, very carefully, and leave the surface of the temporal bones to mop up the moisture with ocular sticks. Next, test if the stimulation electrodes fit onto the cleaned vertical skull surface. The upper edge of the stimulation electrode should be in line with the edge of the cristae of the temporal bone.

Readjust the bulldogs and the retractors or shape the stimulation electrodes with scissors, if necessary. Following that, fill the cavities of the stimulation electrodes with electro-conductive gel, and put a thin layer of glue onto the rim of the electrodes. Place the stimulation electrode on the dry surface of the temporal bone with one accurate movement, and hold it firmly in place for one minute with fine tweezers. Make sure that no moisture is in contact with the glue and mop up with ocular sticks, if necessary.

After that, apply dental cement over the edges of the stimulation electrode while the leaking moisture of the tissues is continuously dried up with ocular sticks. Cover the whole stimulation electrode with cement. After the cement is completely hardened, repeat these steps on the contralateral side. Subsequently, using a 10% smaller diameter drill head compared to the screw diameter, drill some holes all over the skull for anchoring screws.

Drive miniature screws into the holes and apply dental cement over them. Then, continue with implantation of the recording electrodes.

Solder the connectors and anchor them to the construct at the end. Afterward, wash the exposed tissues abundantly with disinfectant. Inject 1% to 2% lidocaine subcutaneously, then, debride wound edges, and close them with simple interrupted sutures around the connector implant. Subsequently, disinfect the wound with povidone-iodine.