Aversive shock generator

The apparatus for Pavlovian fear conditioning consisted of two individual chambers with aluminum front and back walls retrofitted with clear plastic covers, clear acrylic sides and top, and a grid floor. Each grid floor bar was electrically connected to an aversive shock generator (Med Associates, St. Albans, VT) through a grounding device. This permitted the floor to be grounded at all times except during shock delivery. An external food cup and a central nose poke opening, equipped with infrared photocells were present on one wall. Auditory stimuli were presented through two speakers mounted on the ceiling.

The apparatus for Pavlovian fear conditioning consisted of two individual chambers with aluminum front and back walls retrofitted with clear plastic covers, clear acrylic sides and top, and a grid floor. Each grid floor bar was electrically connected to an aversive shock generator (Med Associates, St. Albans, VT) through a grounding device. This permitted the floor to be grounded at all times except during shock delivery. An external food cup and a central nose poke opening, equipped with infrared photocells were present on one wall. Auditory stimuli were presented through two speakers mounted on the ceiling.

Training took place in individual sound-attenuated enclosures that each housed a behavior chamber with aluminum front and back walls, clear acrylic sides and top, and a metal grid floor. Each grid floor bar was electrically connected to an aversive shock generator (Med Associates, St. Albans, VT) through a device that ensured the floor was always grounded apart from during shock delivery. A single food cup and central nose poke opening equipped with infrared photocells were present on one wall. Auditory stimuli were presented through two speakers mounted on the enclosure ceiling. Auditory cues were 10 s in duration and consisted of repeating motifs of a broadband click, phaser, or trumpet, which previous studies have found to be discriminable and equally salient. Testing took place in an identical chamber, but was equipped with a custom plastic food cup, plastic front and back walls, and multi-axis counterbalanced lever arm (Instech Laboratories, MCLA) with plastic tubing that held the recording cable and entered the chamber via a custom plastic top.

The apparatus for Pavlovian fear discrimination consisted of eight, individual sound-attenuated enclosures that each housed a behavior chamber with aluminum front and back walls, clear acrylic sides and top, and a metal grid floor. Each grid floor bar was electrically connected to an aversive shock generator (Med Associates). A single food cup and a central nose poke opening, equipped with infrared photocells, were present on one wall. Auditory stimuli were presented through two speakers mounted on the ceiling of each sound-attenuated enclosure. Behavior chambers were modified to allow for free movement of the optical cables during behavior; plastic funnels were epoxied to the top of the behavior chambers with the larger end facing down, and the tops of the chambers were cut to the opening of the funnel. Green (532 nm, 500 mW) lasers (Shanghai Laser & Optics Century Co, Ltd.) were used to illuminate the DRN. Optical cables were connected to the lasers via 1 × 2 fiber optic rotatory joints (Doric). Rats were bilaterally connected to the optical cables by a ceramic sleeve placed over the implanted ferrule and ceramic ferrule end of the cable. Black shrink-wrap was also placed on the ends of the cables to block light emission into the behavioral chamber. A PM160 light meter (Thorlabs) was used to measure light output.