Single-Neuron Activity Recording Protocol

Neural activity was recorded using a Multichannel Acquisition Processor System (Plexon, Dallas TX, USA) interfaced with Med Associates to simultaneously record behavioral events (Gutierrez et al., 2010 (link)). Extracellular voltage signals were first amplified by an analog head-stage (Plexon, HST/16o25-GEN2-18P-2GP-G1), then amplified and sampled at 40 kHz. Raw signals were band-pass filtered from 154 Hz to 8.8 kHz and digitalized at 12 bits resolution. Only single neurons with action potentials with a signal to noise ratio of 3:1 were analyzed (Gutierrez et al., 2010 (link)). Action potentials were isolated online using a voltage–time threshold window, and three principal components contour templates algorithm. Furthermore, off-line spike sorting was performed (Plexon Offline Sorter), and only single units with stable waveforms across the session were included in the analyses (Gutierrez et al., 2010 (link)) (see Supplementary Figure 1). Also, to verify waveform stability, we correlated the waveform's shapes recorded in the brief access test and the optotagging session.