Model 1474

Extracellular recordings were implemented using 32-channel 10-mm single shank electrodes, where electrode sites were arranged in three columns, spaced 50 microns apart from each other (A1x32-Poly3-10mm-50-177, NeuroNexus, Ann Arbor, MI, USA). Electrodes were inserted into the rodent skull using a small animal stereotaxic frame with 10-micron precision manipulators (Model 963, David Kopf Instruments, Tujunga, CA, USA). Electrodes were inserted at a 40-degree angle in the sagittal plane.
Rodents were sedated using either ketamine/xylazine cocktail for results presented in Figs. 3b–g and 4 or isoflurane for results in Figs. 3a, 5, 6, and 7. All animals were skin prepared with hair removal gel. Rodent heart rate, respiration rates and rectal temperatures were monitored throughout recordings. Cranial windows, 1–2 mm in diameter, were opened in the skull using a high-speed micro drill (Model 1474, David Kopf Instruments, Tujunga, CA, USA) under stereotaxic surgery assisted with microscope system (V-series otology microscope, JEDMED, St. Louis, MO, USA). Skull suture lines were used to identify brain structure locations. Recordings were obtained using the NeuroNexus Smartbox recording system (20 kHz sampling frequency, NeuroNexus, Ann Arbor, MI, USA) and the TDT Neurophysiology Workstation (24 kHz sampling frequency, Tucker-Davis Technologies, Alachua, FL, USA).

Mice were initially anesthetized with 3% isoflurane and maintained at 1–2.5% after placement in the stereotaxic frame (Kopf SD479, Neurostar, StereoDrive). Sterile ophthalmic ointment was applied, and the body temperature was maintained at 37 °C (with the aid of a temperature controller). The scalp was sterilized with ethanol 70% and povidone-iodine before skull exposure. For horizontal plane leveling, the relative dorsoventral displacement of Bregma and Lambda was adjusted to a maximum of 0.05 mm difference. For adjusting tilt, two points equidistant to the left and right of Bregma were used. Craniotomies were made using a hand drill (David Kopf Instruments, Model 1474, drill bit H1.104.008), followed by removal of the underlying dura using a fine needle tip. The brain surface was covered with sterile physiological saline to prevent desiccation.