Smm 200b

We performed extracellular multi-neuronal (multiple, isolated, single-unit) recordings from individual neurons while the rats were performing behavioral tasks. A supportive layer of agarose gel (2% agarose-HGT, Nacalai Tesque, Kyoto, Japan) was placed on the brain, and then 32-channel silicon probes (Iso_3x_tet-A32 or Iso_4x_tet-A32; NeuroNexus Technologies, Ann Arbor, MI, USA) were precisely inserted into CA1 and the LEC. Insertions were performed using fine micromanipulators (SM-15 or SMM-200B, Narishige) at least 1 h before the start of each recording experiment.
Wide-band signals were amplified and filtered (FA64I, Multi Channel Systems, Reutlingen, Germany; final gain, 2000; band-pass filter, 0.5 Hz to 10 kHz) through a 32-channel head stage (MPA32I, Multi Channel Systems; gain, 10). These signals were digitized at 20 kHz and recorded with three 32-channel hard-disc recorders (LX-120, TEAC, Tokyo, Japan) that simultaneously digitized the pedal positions tracked by angle encoders and the events resulting from optogenetic stimulation.

We performed online Multi-Linc experiments in the frontal motor cortices of unanesthetized rats under head-fixation. For the multi-channel recording, we used two 32-channel silicon probes, although the system can accommodate 128 channels. Approximately 1 h before each recording session, the probes were inserted to a depth of 1.0–1.5 mm from the cortical surface, typically in layer 5, where intratelencephalic (IT)-type projection neurons are distributed most abundantly, using three-axis micromanipulators (SMM-200B and SMM-100, Narishige). On the last recording day, the probe tracks were marked with the red fluorescent dye DiI (DiIC18(3), PromoKine, Heidelberg, Germany) applied to the back of each shank for histological conformation. In the optogenetic stimulation, we used micromanipulators (SM25A, Narishige) to place two to six optic fibers (FT1000EMT, diameter: 1000 μm, Thorlabs, New Jersey, USA) on the cortical surface in a symmetrical position contralaterally from the silicon probes.