Stereotactic Implantation of Microdrives

We stereotactically implanted two microdrives in each bird. The electrodes were positioned in NCL [anteroposterior (AP), +5.0; mediolateral (ML), –7.5; dorsoventral (DV), –1.5] and NIML (AP, +9.5; ML, –3.5; DV, –2.3) of the right hemisphere (Karten and Hodos, 1967 ). Coordinates for the regions were based on histologic studies on the localization of NCL (Waldmann and Güntürkün, 1993 (link); Herold et al., 2011 (link)) and NIML (Rehkämper et al., 1985 (link)). The birds were anesthetized using isoflurane and received meloxicam (2 mg/kg, i.m.) for analgesia. The skull was exposed, and small craniotomies were made over the target structures. Electrodes and microdrives were fixated with dental acrylic to small bone screws, one of which served as a ground for the recordings. After surgery, the birds received several days of recovery, with monitoring and analgesic treatment of butorphanol (1.5 ml/kg, i.m.). In one of the birds, the left hemisphere was also implanted with the same coordinates in a separate surgery.