Designs and predictions for each experiment in the series

The neural substrates of the mediated S2-shock and direct S1-shock associations that form in stage 2 of sensory preconditioning are doubly dissociable at the level of NMDAR-activation in the PRh and BLA.

(A, C) Schematics of the protocols used to assess the involvement of NMDAR in acquisition of freezing to S2 and S1 in the PRh (Experiment 1A) and BLA (Experiment 1B). The protocols differed only in whether rats received an infusion of the NMDAR antagonist, DAP5, into the PRh (in A) or BLA (in C). (B) Test results showing that a stage 2 infusion of DAP5 into the PRh disrupts freezing to S2 without affecting freezing to S1. (D) Test results showing that a stage 2 infusion of DAP5 into the BLA disrupts freezing to S1 without affecting freezing to S2. The bars in each histogram show the mean level of freezing in each group across repeated presentations of S2 or S1 under conditions of extinction. The error bars show the standard error of the mean, and the overlaid data points represent the mean level of freezing for individual rats. The final group sizes were n = 10 for Group VEH and n = 11 for Group DAP5 in Experiment 1A; and n = 15 for Group VEH and n = 13 for Group DAP5 in Experiment 1B.

Combining the S2-S1 and S1-shock pairings into S2-S1-shock sequences alters the substrates of conditioning to the S2 in the PRh and BLA.

(A, C) Schematics of the protocols used to assess when NMDAR are involved in acquisition of freezing to S2 and S1 in the PRh (Experiment 2A) and BLA (Experiment 2B). The protocols differed only in whether rats received an infusion of the NMDAR antagonist, DAP5, into the PRh (in A) or BLA (in C). (B) Test results showing that a stage 2 infusion of DAP5 into the PRh has no effect on levels of freezing to either S2 or S1. (D) Test results showing that a stage 2 infusion of DAP5 into the BLA disrupts levels of freezing to both the S2 and S1. The final group sizes were n = 8 for Group VEH and n = 9 for Group DAP5 in Experiment 2A; and n = 8 for Group VEH and n = 9 for Group DAP5 in Experiment 2B.

Pre-exposing rats to S2-S1 pairings prior to a session of S2-S1-shock sequences re-engages NMDAR in the PRh for conditioning of the S2.

(A, C) Schematics of the protocols used to assess when NMDAR are involved in acquisition of freezing to S2 and S1 in the PRh (Experiment 3A) and BLA (Experiment 3B). The protocols differed only in whether rats received an infusion of the NMDAR antagonist, DAP5, into the PRh (in A) or BLA (in C). (B) Test results showing that a stage 2 infusion of DAP5 into the PRh disrupts freezing to S2 without affecting freezing to S1. (D) Test results showing that a stage 2 infusion of DAP5 into the BLA disrupts freezing to S1 without affecting freezing to S2. The final group sizes were n = 12 for Group VEH and n = 12 for Group DAP5 in Experiment 3A; and n = 10 for Group VEH and n = 10 for Group DAP5 in Experiment 3B.

Pre-exposing rats to S2-S1 pairings prior to a session of S2-[trace]-shock pairings re-engages NMDAR in the BLA for conditioning of the S2.

(A, C) Schematics of the protocols used to assess when NMDAR are involved in acquisition of freezing to S2 and S1 in the PRh (Experiment 4A) and BLA (Experiment 4B). (B, D) Test results showing that a stage 2 infusion of DAP5 has no effect on the level of freezing to S2 when injected into the PRh (in B) but disrupts the level of freezing to S2 when injected into the BLA (in D). The final group sizes were n = 14 for Group VEH and n = 15 for Group DAP5 in Experiment 3A; and n = 12 for Group VEH and n = 14 for Group DAP5 in Experiment 3B.

Cannula placements in the PRh for rats in Experiments 1B, 2B, 3B and 4B.

The most ventral portion of the cannulas are marked on coronal sections based on the atlas of Paxinos and Watson (2006).

Cannula placements in the PRh for rats in Experiments 1A, 2A, 3A and 4A.

The most ventral portion of the cannulas are marked on coronal sections based on the atlas of Paxinos and Watson (2006).