To begin, make an electrocorticography or ECoG headset by soldering perfluoroalkoxy-coated stainless steel wire to a three-pin connector header. After identifying the insertion coordinates based on a mouse stereotaxic atlas, position the anesthetized mouse in the stereotaxic frame. Place the animal's nose in the nose cone and stabilize the head with head bars.
Then perform a toe pinch test to check the depth of anesthesia. After making a five-millimeter scalp incision above the parietal and occipital bones, scrape the meninges with the scalpel blade to remove them. Use the scalpel blade to cut muscle attachments and expose the parietal and occipital bones.
Apply hydrogen peroxide to control bleeding and dry the skull surface. Next, identify the bregma and lambda landmarks on the skull. Then adjust the nose cone position to level the anterior-posterior position of the skull.
To level the medial lateral position of the skull, pick two opposite points between bregma and lambda and check their level. Now, measure the distance between bregma and lambda and compare it to the distance reported in the Franklin Paxinos Stereotaxic Atlas. Use the difference between the measured and reported distances to scale the anterior-posterior coordinate proportionally.
Mark craniotomy coordinates on the skull with a sterilized pencil. Using a stereotaxic micro manipulator, position the headplate directly on top of the lambda suture. Apply dental cement to the headplate and around it to secure it to the skull and allow it to dry for 10 minutes.
Then drill burr holes for two cortical electrodes and one reference electrode. Place the stripped ends of coated silver wire electrodes within the burr holes and secure them using ultraviolet light activated resin. Completely cover the coated stainless steel wires with dental cement so that no wire is exposed.
Cover the underside and sides of the headset with dental cement to ensure it is firmly in place and allow the mouse to recover for seven days.
