Env 200r2m

Polycarbonate test boxes (24 cm wide, 25 cm deep, by 26 cm tall) were equipped with a steel rod floor (ENV-013WR, Med Associates, Fairfax VT) and two identical operant levers (ENV-110RM, Med Associates, Inc., Fairfax VT). Responding on both levers was recorded, but only left-hand (active) responses led to reinforcement. A pneumatic syringe (model 100; IITC, Inc., Woodland Hills, CA) was mounted on each box to deliver reinforcement with either intravenous cocaine hydrochloride (donated by the National Institute on Drug Abuse) or liquid food (Ensure® original vanilla, Abbott Laboratories, Abbott Park, IL). In either case, rats were tethered to an overhead fluid swivel (375/22; Instech, Plymouth Meeting, PA) using a flexible steel cable (C313CS/SPC, Plastic One). Because tethering can alter operant behavior, it was used during responding for either reinforcer to ensure comparable results. Food reinforcement was delivered to a liquid trough (Env-200R2M, Med Associates) mounted at a height of 4.5 cm. Experiments were controlled by a DIG-700P1 interface with custom programing written in Med PC software (version 1.15, Med Associates). Outside disturbances were minimized by enclosing boxes within sound attenuated chambers equipped with ventilating fans to provide white noise.

Training and testing were conducted in operant conditioning chambers controlled by WMPC software (Med Associates, VT), and enclosed in sound-attenuating boxes with fans for ventilation. As in our previous studies (Wood et al, 2016 (link); Li and Wood, 2017 (link)), operant chambers were divided in half by a removable mesh screen (0.5 cm grid). Each side of the chamber was equipped with a retractable lever (ENV-112CM, Med Associates) and stimulus light (ENV-229M) adjacent to a food trough (ENV-200R2M) connected to a pellet dispenser (ENV-203–45). For Stooges, the levers extended and retracted, but responses on the levers had no consequence and were not recorded. Instead, Stooge responses were controlled by computer according to the TFT, WSLS, or random strategy, and pellets were delivered to Subject and Stooge according to the payoff matrix of the game (IPD or Stag Hunt). A house light (ENV-215M) and clicker (ENV-135M) were mounted in the center of the ceiling.

The operant behavior testing (OBT) components were obtained from Med Associates, Inc. (Fairfax, VT): nose poke (ENV-114AM), cue light (ENV-221M), tone generator (ENV-223AM), pellet dispenser (ENV-203) and pellet receptacle (ENV-200R2M). Lithium-Ion batteries (12 V, 10 Ah Model: CR12V10Ah with BMS protection circuit) were purchased from Dakota Lithium Battery (Seattle, WA). An MD-ROOC uses one battery at a time. A bidirectional digital I/O interface (NI 9401), wireless data acquisition unit (cDAQ 9191) and interface software (LabVIEW 2016) originated from National Instruments (Austin, TX). The wireless-LAN router (E1200 N300 Wi-Fi Router) was from Linksys (Irvine, CA). The battery delivers the power for all OBT and National Instruments components. A locally constructed digital interface contains an in-house built printed circuit board that accepts digital inputs to control MedAssociates components as well as receiving signals from the nose poke. (Supplementary Information Figures S.1–3).
Ordinarily, OBT componentsuse 28 V for both power and control signals. However, they can be configured, or modified, to use 12 V signals instead. Table 1 lists the modifications neccessary to allow the OBT components to be operated at 12 V.