(A) Timeline of behavioral testing. After 2 days of baseline startle testing, female (N = 72) and male (N = 72, N = 12/group) rats were given an initial contextual fear conditioning session (Training 1) consisting of two shocks presented either within seconds after placement into the conditioning chamber (immediate) or after a 6-min acclimation period (delayed). 1 h, 1 day, or 1 week later, rats received a second conditioning experience consisting of a single light-shock. Long-term memory to the context and light cue was tested 48 h later, with the light cue tested first and the context tested the next day. (B) Males showed higher average baseline startle than female rats (P < 0.05). (C) Freezing behavior in the 2-min period after shock in which there was a significant effect of sex (P < 0.01) and training type (P < 0.0001). (D) No significant differences were observed in shock reactivity during visual fear conditioning. Error bars = ±SEM; dots = individual means.
