Electrode positioning system and multi channel processor

We performed extracellular recordings from PCs using glass-coated tungsten microelectrodes (impedance: 1 to 2 MΩ) that were purchased from Alpha Omega Engineering, Nazareth, Israel. The position of the electrodes, which were targeted toward the OMV, was controlled using a modular multielectrode manipulator (Electrode Positioning System and Multi-Channel Processor, Alpha Omega Engineering). The identity and the exact coordinates of the OMV predicted by the MRI scans were confirmed by physiological criteria, i.e., the presence of a dense saccade-related background activity, reflecting multiunit granule cells activity. To differentiate action potentials from the underlying LFP signals, extracellular potentials, recorded at the sampling rate of 25 KHz, were high band-pass filtered (300 Hz to 3 KHz) and low-pass filtered (30 Hz to 400 Hz), respectively. A total of 160 PCs were recorded out of which 151 were considered for analysis. A table summarizing the total number of PCs recorded from each monkey, either in left, right, or both directions, can be found in S1 Table.