Surgical Implantation of EMG Electrodes for Eyeblink Conditioning in Mice

The surgical procedures were the same as in our previous study [19 (link)]. In brief, mice were anesthetized with ketamine (80 mg/kg, i.p.; Sankyo, Tokyo, Japan) and xylazine (20 mg/kg, i.p.; Bayer, Tokyo, Japan). During surgery, isoflurane (1–2%, Abbot Japan, Osaka, Japan) was used when necessary. Four Teflon-coated stainless-steel wires (140 μm in diameter, A-M Systems, Sequim, WA, USA) were subcutaneously implanted in the left upper eyelid. Two of them were used to record EMGs for the CR detection and the remaining two to deliver electrical shocks as the US. The connector pins soldered to the wires were fixed to the skull with the help of dental acrylic resin and stainless steel screws. Subsequently, mice were injected with ampicillin (100 mg/kg, i.p.; Meiji Seika, Tokyo, Japan), placed in a warm cage until they moved voluntarily, and then returned to their home cage.