Microdrive placement. a, b, Photographs of a fully constructed microdrive with four drive axes. c–i, Chronological photographs from a microdrive placement procedure with the following four nonparallel, separated drive axis targets: VLPO, DR, PPT, and LDT. c... Microdrive placement. a, b, Photographs of a fully constructed microdrive with four drive axes. c–i, Chronological photographs from a microdrive placement procedure with the following four nonparallel, separated drive axis targets: VLPO, DR, PPT, and LDT. c, The microdrive is attached to a custom 3D-printed placement tool, which can be manipulated by the stereotaxic device. d, Petroleum-jelly plugs, highlighted by the four black arrows, are first removed from the skull-fixed guide cannulas. Leads of the accessory electrodes, which include cortical screws and hippocampal depth electrodes, are taped down to the side of the headmount base for later riveting. e, f, The microdrive is lowered with the stereotaxic device, and the placement tubes of each drive axis are inserted into the skull-fixed guide cannulas, one of which is highlighted with a black arrow in f. The placement tubes are guided using customized forceps that have small notches near the tips to grab and manipulate the tubes without crushing them. g, All four placement tubes are engaged with their respective guide cannulas. h, The placement tubes are closer to being in complete position. Once the drive axes are in place, the bottom of the body tube, which is highlighted with black marker, will be seated on top of the guide cannula. i, After all the drive axes are seated, the microdrive is secured to the headmount base with the foot screws and the placement tool is removed. Finally, the cortical screw and depth electrode leads are riveted into the EIB. Myles W. Billard et al. eNeuro 2018;5:ENEURO.0261-18.2018 ©2018 by Society for Neuroscience