Multielectrode Hippocampal Recordings

We built microelectrode arrays (16 electrodes, 50 μm diameter Teflon-coated tungsten wires, California Fine Wire) designed to target the dorsal hippocampus of both hemispheres [−3.6 mm AP, ± 3.0 mm ML, according to Paxinos and Watson (2013) ]. Electrodes were arranged in two 1 × 8 bundles with an inter-electrode lateral spacing of 250 μm, and an inter-electrode depth difference of 200 μm creating a stair design (Figure 1A). The eight microelectrodes were distributed across the laminar profile of the hippocampus (from 2.1 to 3.6 mm DV) to record electrophysiological signals from CA1, CA3, and DG from both hemispheres. The electrode impedance was reduced to ∼0.5 MOhms at 1 kHz in a gold solution with carbon nanotubes using NanoZ (Neuralynx) previously to surgery in accordance with previous studies (Ferguson et al., 2009 (link)).