Cued and Contextual Fear Conditioning in Mice

Mice underwent cued and contextual fear conditioning, as previously described [24 (link)]. Briefly, on conditioning day, mice were allowed to explore the conditioned context, which consisted of a Plexiglas chamber and metal floor grid (model H10-11M; Coulbourn Instruments, Whitehall, PA, USA). After 3 min, 15 s of white noise (80 dB) was presented co-terminating with a 2 s, 0.75 mA foot shock. This noise-shock pairing was repeated twice for a total of 3 shocks with a 30 s interval between shocks. Twenty-four hours later, mice were re-exposed to the conditioning chamber for 5 min and freezing responses were measured using FreezeView Software (Coulbourn Instruments) to test contextual long-term memory. Four hours later, mice were placed in a novel context consisting of a 15 cm open-topped plastic cylinder with bedding on the floor for 3 min followed by re-exposure to the white noise for 3 min, to test hippocampal-independent memory. All data were video recorded using FreezeFrame Video-Based Conditioned Fear System and analyzed by FreezeView Software (Coulbourn Instruments). CFC was performed in all male mice before female mice.