Threat Conditioning and Extinction in Rats

Threat conditioning and extinction tasks were performed as previously described (Martínez-Canabal et al., 2019 (link)). Briefly, auditory threat conditioning and extinction was performed in standard operant chambers (Coulbourn Instruments) located inside sound-attenuating boxes (Med Associates) in an isolated testing room. The floor of the operant chambers consisted of stainless-steel bars that could deliver electric foot-shocks. Between experiments shock grids, floor trays and walls were cleaned with soap and water. On day 1, rats were subjected to threat conditioning consisting of five tone presentations (30 s, 4 kHz, 75 dB) that co-terminated each one with a foot-shock (0.5 s, 0.6 mA). On day 2, after conditioning, rats received extinction training consisting of fifteen presentations of unreinforced tones. On day 3, rats were tested for memory retrieval with two tone-alone presentations. In all sessions, the interval between tones was variable with an averaged 2 min.