Implantation of Electrodes into a Mouse Cortex for Electrocorticographic Recordings

Take an anesthetized mouse with its skull exposed on a stereotactic frame. This mouse has been injected with a virus expressing the mutated actin-severing protein into the right cerebral cortex.

Screw an electrocorticographic electrode into the injection site.

Mark and drill the skull perpendicularly for the posterior electrode, reference electrode, and maintenance screws.

Disinfect the sites with antiseptic and block them to prevent bleeding.

Insert the screws and electrodes at the same drill angles and apply dental cement to the space between them.

Now, use light to solidify the cement.

Cover the bases of the electrodes and screws with dental cement and apply light again. Secure the assembly with acrylic cement. Suture the skin.

Connect the electrodes' gold wires to the connector pins.

Cover the connector space with acrylic cement.

Allow the mouse to recover. Following recovery, record cerebral cortex signals in response to the viral injection.

For electrode implantation, use straight Kelly forceps to slowly screw one electrocorticographic electrode with a straight gold wire, into the vertical axis of the hole in which the AAV was injected, leaving at least 2.5 millimeters of screw outside of the skull to minimize the damage to the dura and the cerebral cortex.

Use a pen to mark the position of the reference electrode 2.6 millimeters lateral right to the midline and 0.7 millimeters posterior to bregma, and the position of the posterior electrocorticographic electrode at 1.5 millimeters lateral right to the midline and 1.5 millimeters anterior to lambda, and the positions of three maintenance screws on the left hemisphere with no specific coordinates, but as distant as possible from each other and from the electrocorticographic electrodes.

Use the drill to carefully pierce the skull perpendicular to the skull surface at the marked positions of the other electrodes and screws, and wash the pierced skull with a 10% povidone-iodine solution.

Block the holes with small rolled pieces of delicate task wipe before installing the screws to prevent bleeding and contamination, and use straight Kelly forceps to insert the screws into the drill holes at the same angle that the holes were pierced. Place a few small drops of dental cement into the center of the ring-like space inside the screws. After covering the eyes of the animal, apply light for three to five minutes to solidify the cement, and use additional dental cement to cover the base of the electrocorticographic electrodes, and the anchor screws to form a crown-shaped contour.

After applying three to five more minutes of light, fill the center of the montage with acrylic cement, and remove the surgical clamps.

Use a synthetic absorbable monofilament suture to close the skin at the front and back of the montage so that the skull is not exposed, and use curved forceps to hold the connector above the montage to carefully align the gold wires of the electrodes with the connector pins. Then, quickly solder each electrode extremity to a single corresponding connector pin.

After removing the mouse from the frame, cover the empty space between the connector and the head with the acrylic cement, and after weighing, place the mouse in a clean cage with a non-meshed lid on a heat pad.