Extracellular cell firing recorded from carbon-fiber electrodes (impedance at the tip: ~500 k3 at 1 KHz sine wave in saline) were amplified (x1000) and bandpass-filtered (300 Hz to 3 KHz). The units were digitized with commercially available software (Neurosurgery WorkStation, Plexon Inc, Dallas, TX). The waveforms were discriminated using principal component analysis in Offline Sorter (Plexon Inc, Dallas, TX). One to two neurons could typically be discriminated at each location. Custom-written software (LabVIEW, National Instruments, Austin, TX) was used to timestamp each behavioral event to the electrochemical record allowing analysis of relationships among behavior, dopamine release events and NAc cell firing.
