Virus-infected (eYFP+) cells were identified using scanning disk confocal microscopy (Olympus FV1000), and differential interference contrast optics were used to patch neurons. Whole cell current clamp recordings were performed in visually identified neurons in the orbitofrontal cortex. For NpHR experiments, a 593 nM laser (OEM laser systems; maximum output 150 mW) attached to fiber optic cable was used to deliver light to the slice. Light intensity of 8 -12 mW was used to stimulate NpHR in slice recordings. For experiments shown in Figure 6A,a 10 s light pulse was delivered to the slice. For experiments shown in Figure 6B, current pulses were injected (500 ms square pulse, 50 pA-600 pA). Half of the time, a 500 ms light pulse was given during current injection. Images were acquired using Olympus Fluoview software (version 3.0). Electrophysiology **data** were acquired using an Axopatch 200 B amplifier (Molecular Devices, San Jose, CA) in either voltage clamp or current clamp mode. Axograph X software (Axograph Scientific) were used to record and collect the data, which were filtered at 10 kHz and digitized at 4 -20 kHz. Series resistance (Rs) was monitored with injection of hyperpolarizing current (À20 pA, 500 ms) and **data** were excluded if Rs changed >20% during **data** acquisition. Recordings were discarded if series resistance or input resistance changed >10% throughout the course of the recording.