Graphic state software

During the first session of SAA training, rats were presented with a single Pavlovian trial in which the CS was paired with the US in a way that could not be avoided, in order to ensure that the tone would be associated with the shock. The rest of training consisted of avoidance trials in which an avoidance response (shuttling during the CS) would result in the immediate offset of the CS and the omission of the US. The rats received 30 avoidance trials during each SAA training session. Between each trial was an ISI that averaged 120 seconds. CS and US presentation were controlled by GraphicState Software (Coulbourn Instruments), which also collected shuttling data via the infrared arrays in each compartment. Rats were considered poor avoiders and excluded from the statistical analyses if they avoided on ≤ 20% of trials for the last 3 days of training.

The delay discounting task was conducted in standard behavioral test chambers (Coulbourn Instruments, Whitehall, PA) housed within sound-attenuating isolation cubicles. Each chamber was equipped with a recessed food pellet delivery trough fitted with a photobeam to detect head entries and a 1.12 W lamp to illuminate the food trough, which was located 2 cm above the floor in the center of the front wall. Forty-five mg grain-based food pellets (PJAI, Test Diet, Richmond, IN) could be delivered into the food trough. Two retractable levers were located to the left and right of the food trough, 11 cm above the floor. A 1.12 W house light was mounted on the rear wall of the isolation cubicle. Locomotor activity was assessed throughout each session with an infrared activity monitor mounted on the ceiling of the test chamber. This monitor consisted of an array of infrared (body heat) detectors focused over the entire chamber. Movement in the chamber (in x, y, or z planes) was defined as a relative change in the infrared energy falling on the different detectors in the array. Test chambers were interfaced with a computer running Graphic State software (Coulbourn Instruments), which controlled programmed events and data collection.

Seven Coulbourn^®Habitest (Coulbourn Instruments, Whitehall, PA, USA) standard experimental chambers for rats were used for data collection. Each chamber was equipped with two levers and stimulus lights situated on the right side of the chamber and 5 cm above the grid floor. Only the right stimulus light was illuminated and the right lever was active during each session. When a response contingency was met, a 45-mg grain-based Precision pellet (Bioserv, Frenchtown, NJ; 3.35 kcals/g) was dropped into a food receptacle situated between the two response levers. White noise was generated via a speaker situated on the top-right corner of the left wall. The chamber was ventilated via a 5 cm × 5 cm fan on the top-left corner of the left wall. Each chamber was placed in a sound-attenuating cubicle. Experimental events were controlled and data were collected with a 0.01-s resolution using GraphicState^® software (Coulbourn Instruments, Whitehall, PA, USA) on a Windows-based computer.

Rats were trained and tested in standard operant chambers (Coulbourn Instruments; Whitehall, PA, USA) that were housed inside sound-attenuating cubicles. The cubicles were equipped with fans that provided ventilation and masked extraneous noise. One wall of each operant chamber was equipped with a centrally located food trough outfitted on either side with a response module (retractable levers in Exp. 1, Exp. 2; recessed nosepoke ports in Exp. 3) that were equidistant (87 mm) from the trough. White cue lights were located above each response module and a white houselight was located near the chamber ceiling on the wall opposite the food trough. Sessions were recorded and analyzed using Graphic State software (Coulbourn Instruments; Allentown, PA).

Seven Coulbourn® Habitest (Coulbourn Instruments, Whitehall, PA, USA) rat operant chambers were used for data collection. Chambers were equipped with two levers on the right sidewall panel and were 5 cm above a grid floor with a food alcove centered between the levers. When response requirements were met, and depending on the experimental condition, one or more 45-mg sucrose pellets (95% sucrose, 3.4 kcal/g; TestDiet®, Richmond, IN, USA) or carrot-flavored pellets (3% sucrose, 3.3 kcal/g; TestDiet®, Richmond, IN, USA) were delivered to the alcove. These pellet types were chosen because these same carrot-flavored pellets were less preferred than sucrose pellets in Sprague-Dawley rats and Zucker rats in a previous study (see Buckley & Rasmussen, 2012 (link)). Two 28-V stimulus lights were situated above each lever as well as a 28-V houselight that was 28 cm above the alcove. A 5 cm X 5 cm fan circulated air in the upper left corner of the left sidewall panel and white noise was generated from a speaker in the upper right corner of the left sidewall panel. Each chamber was placed in a sound-attenuating cubicle and Graphic State® software (Coulbourn Instruments, Whitehall, PA, USA) on a Windows-based computer (located in an adjacent room) controlled all data collection within 0.01-s resolution.