Wide range of fear responses to the testing context following fear conditioning. (A) Schematic representation of the experiment. Animals were habituated to context A for 3 d (5 min/day), received two tone–shock pairings in context B, and were tested by presenting the tone without shock in context A 24 h later. (B) Average individual freezing before (pre-CS) and during (CS) tone presentation during the testing session. Wilcoxon matched-pairs signed rank test: pre-CS versus CS, W = 262. (***) P < 0.001. (C) During the 2 min preceding presentation of the tone (pre-CS phase) in context A, there was an overall unexpected widening of fear responses to the context. Horizontal dashed lines indicate cutoff at 10%. (D) Freezing (in percentage) to context B before the first tone–shock pairing (Pre phase) at the training session was minimal. Same cutoff as in C is indicated.
