Lister hooded rats

The subjects were 120 adult male Lister hooded rats (Charles River, UK) weighing 275–325 g. Rats were housed in pairs with food and water access ad libitum. The holding room was maintained at 21°C with a 12 h reversed light/dark cycle. Subjects were given at least 5 days to acclimatise to the holding room prior to testing. The handling of animals from each experimental group was ordered pseudorandomly. All procedures were conducted in accordance with the local Cardiff University Ethical Committee approval and the United Kingdom 1986 Animals (Scientific Procedures) Act.

Subjects were 16 male Lister Hooded rats (Charles River, Margate, UK). Two rats did not complete judgement bias (JB) testing due to poor performance in training; they did not reach the progression criterion at the discrimination stage of training (see: Jones et al. (2018)^{25 (link)}). The rats were housed in stable pairs in cages measuring 560x340x190mm and kept under a 12-h reverse light cycle, with lights off at 7am and on at 7pm. Two cardboard tubes and an aspen block were provided as enrichment and subjects had ad libitum access to food (LabDiet) and water. This research received ethical approval from the Animal Welfare and Ethical Review Body at the University of Bristol (UIN: UB/16/004) and adhered to ASAB/ABS guidelines for the use of animals in research. Subjects were rehomed as pet rats on completion of the experiment.

Subjects were 25 male Lister Hooded Rats (Charles River Ltd, UK) weighing between 330 and 400 g at the time of surgery. They were group-housed in a room held at a temperature of 21°C under a 12 h light/dark cycle (lights off 7 P.M.). Following recovery from surgery, water was available ad libitum and food (laboratory chow, Purina) was restricted to 20 g laboratory chow/day, sufficient to maintain 90% pre-operative body weight. All experiments were carried out during the light phase, between 08:00 and 18:00 h and in accordance with the United Kingdom 1986 Animals (Scientific Procedures) Act Project License no. 30/2561.

Thirty-two male Lister hooded rats (Charles River, UK) were housed in pairs in 25 × 45 × 15-cm plastic cages. Testing was conducted in the light phase of a 12-h light/dark cycle (lights on at 7:00 am). The rats were maintained on a restricted diet (15–20 g of food per day) with water freely available in the home cage. We adhered to the guidelines laid out in the Principles of Laboratory Animal Care (National Institutes of Health, Publication No. 86-23, revised 1985) and the requirements of the United Kingdom Animals (Scientific Procedures) Act 1986.

Subjects were 117 male Lister-Hooded rats (Charles River), weighing 200–250 g at the start of the experiment. Rats were housed in cages of four at 21°C on a 12-h light–dark cycle (lights on at 07.00) and fed a restricted diet of 15 g/d. Water was available ad libitum. All procedures were approved by a local ethical review committee and carried out in accordance with the United Kingdom 1986 Animals (Scientific Procedures) Act (PPLs 40/3205 & 70/7662).
Twenty-four rats were used in order to test the ability of brief nonreinforced reactivation to destabilize memory. A further 64 rats were used in the VR20 reactivation study and accompanying nonreactivated control, split into MK-801 and saline treated groups. Finally, 29 rats were used for an FR20 reactivation. Groups were initially divided into drug and control treatment groups, which were then each further subdivided into outcome-valued and -devalued groups. A subset of VR20 reactivated rats was given contingency testing, and was subdivided into yoked and omission groups for the omission testing. No rats were excluded from any experimental group.

Subjects were 219 experimentally naïve adult male lister hooded rats (Charles River), aged 6-8 weeks (median 6 weeks) and weighing 200-350 g (median 250 g) at the start of the experiment. Rats were housed in individually-ventilated cages of 4 at 21 °C on a 12 h light-dark cycle (lights on at 0700) in a specialist animal facility. Individually-ventilated cages contained aspen chip bedding, and environmental enrichment was available in the form of a Plexiglass tunnel. Experiments took place in a behavioral laboratory between 0800 and 1200. Rats in the sucrose studies were fed a restricted diet of 15 g chow per day for the duration of the behavioral procedures (this was supplemented by any sucrose rewards obtained during the study); weights were regularly recorded and assessed against an in-house growth chart. Rats in the cocaine study had freely available food. Water was freely available except during experimental procedures. At the end of the experiment, animals were humanely killed via a rising concentration of CO₂; death was confirmed by cessation of heartbeat. All procedures were approved by a local ethical review committee and carried out in accordance with the United Kingdom 1986 Animals (Scientific Procedures) Act (PPLs 40/3205 & 70/7662).