2.4. EEG electrode implantation surgery

EEG electrode implantation surgery was performed at day 0 under anesthesia using methodology previously described. ³ , ¹⁹ Briefly, animals were anesthetized using 5% isoflurane, and Polyvisc was applied to the eyes. The skull fur was shaved, and the skin was cleaned. A midline incision was made on the scalp, and four burr holes were drilled through the skull without penetrating the dura: one on each side of the frontoparietal region (AP: ±1.7; ML: −2.5) and two on each side of the temporal region (AP: ±5. 6; ML: left 2.5). Four epidural stainless‐steel screw recording electrodes (EM12/20/SPC) were screwed into the burr holes. Ground and reference epidural stainless‐steel screw electrodes were implanted on each side of the parietal bone above the cerebellum. Recording electrodes were fixed in position by applying self‐curing dental cement, and the incision was then sutured.

Immediately after surgery, each animal received an injection of buprenorphine (0.05 mg/kg i.p.) for analgesia and 3 mL of 0.9% NaCl solution every 12 h for 2 days to prevent dehydration. The animals were allowed to remain on a heat pad overnight. Rat mush (40% coarse ground rat pellet, 40% rodent milk powder, and 20% sterile water) was given to the animals for up to 5 days. The weight, grooming, and movement of the animals were monitored every 8 h for the first 2 days after the surgery, then twice daily for 5 days (see below).