Freezeframe 3

The data were collected and scored using FreezeFrame3 software (Actimetrics, Wilmette IL). The bout length was set to 0.75-s and the freezing threshold (changes in pixels per frame) was adjusted by an experimenter so that no small movements were registered as freezing.

The apparatus and stimuli used have been described previously [37 (link),46 (link)]. Briefly, fear conditioning occurred in four clear Plexiglas chambers arranged in a 2 × 2 formation on a Plexiglas stand within a fume hood (Context A – Pre Group). Each chamber had a grid floor made of nine stainless steel bars connected to a shock scrambler (Med Associates, Georgia, VT-ENV-414S). The alternate context (Context B – Alt-Pre Group) consisted of the same Plexiglas chambers with a convex wire mesh insert that covered the back wall and floor of the chamber and a white paper sleeve that covered the outside walls of the chamber. In Experiment 1B, 2, and 3, the unconditioned stimulus (US) was two, 1.5 mA foot-shocks, each 2s in duration, and presented 1s apart immediately upon chamber entry. In Experiment 1A, one immediate shock was given instead of two. Videos of each session (preexposure, training, testing) were recorded using Freeze-Frame 3.0 software (Actimetrics, Wilmette IL) with freezing defined as a bout of 0.75 s or longer without a change in video pixilation (see section 2.8.2).

The apparatus and stimuli used have been previously described [12 (link),13 (link),19 (link)]. Fear conditioning occurred in four Plexiglas chambers measuring 16.5 cm × 12.1 cm × 21.6 cm which were arranged in a 2 × 2 formation on a Plexiglas stand within a fume hood to provide ambient light and background noise (Context A). Each chamber had a grid floor made of 9 stainless steel bars (11.5 cm from the top of the chamber), 0.5 cm in diameter and spaced 1.25 cm apart. The alternate context (Context B) consisted of the same Plexiglas chambers with a convex wire mesh insert that covered the back wall and floor of the chamber and a white paper sleeve that covered the outside walls of the chamber. Footshock was delivered using a shock scrambler (Med Associates, Georgia, VT ENV-414S) connected to the grid floor of the chamber. The fear chambers were cleaned with 5% ammonium hydroxide solution prior to each load of experimental animals. Videos of each session (preexposure, training, testing) were recorded using Freeze Frame 3.0 software (Actimetrics, Wilmette IL) with freezing defined as a bout of 0.75 s or longer without a change in video pixilation as previously described [13 (link)].

The apparatus and stimuli used have been previously described (Heroux et al., 2016 (link), 2017 ; Murawski & Stanton, 2010 (link); Robinson-Drummer, Dokovna, Heroux, & Stanton, 2016 (link)). Fear conditioning occurred in four clear Plexiglas chambers measuring 16.5 cm × 12.1 cm × 21.6 cm, which were arranged in a 2 × 2 formation on a Plexiglas stand within a fume hood to provide ambient light and background noise (Context A). Each chamber had a grid floor made of nine stainless steel bars (11.5 cm from the top of the chamber), 0.5 cm in diameter and spaced 1.25 cm apart. The alternate context (Context B) consisted of the same Plexiglas chambers with a convex wire mesh insert that covered the back wall and floor of the chamber and a white paper sleeve that covered the outside walls of the chamber. The unconditioned stimuli (US) was two, 1.5 mA foot-shocks, each 2 s in duration, and presented 1 s apart. These were delivered using a shock scrambler (Med Associates, Georgia, VT ENV-414S) connected to the grid floor of the chamber. The fear chambers were cleaned with 5% ammonium hydroxide solution prior to each load of experimental rats. Videos of each session (preexposure, training, testing) were recorded using Freeze Frame 3.0 software (Actimetrics, Wilmette IL) with freezing defined as a bout of 0.75 s or longer without a change in video pixilation.

The apparatus and stimuli used have been described previously [55 (link),60 ,63 (link)]. Briefly, fear conditioning occurred in four clear Plexiglas chambers within a fume hood (Context A – Pre group), with grid floors connected to shock scramblers (Med Associates, Georgia, VT-ENV-414S). The alternate context (Context B – Alt-Pre group) consisted of the same Plexiglas chambers with a convex wire mesh insert that covered the back wall and floor of the chamber and a white paper sleeve that covered the outside walls of the chamber. The unconditioned stimulus (US) was two, 1.5 mA foot-shocks, each 2s in duration, and presented 1s apart immediately upon chamber entry. Videos of each session (preexposure, training, testing) were recorded using Freeze-Frame 3.0 software (Actimetrics, Wilmette IL) with freezing defined as a bout of 0.75 s or longer without a change in video pixilation.