Figure 1. Overview of experiment design.

Prior to the main two-phase incidental encoding task, participants performed a functional localizer task in which they viewed mini-blocks of neutral scenes and scrambled images (green box). Next, participants performed Phase 1 of a two-phase incidental encoding task. During this first phase (preconditioning; blue), participants viewed a series of neutral animal and tool images and had to classify the category of each image via button press. Importantly, four neutral scene images were also inserted in between each tool and animal image to create a unique ‘context tag’ for Phase 1 information. Approximately 6 minutes later, participants incidentally encoded novel animal and tool images (Phase 2; gold box). This time, however, a mild electrical shock also co-terminated with 2/3rds of the trials from one visual category (conditioning), thereby making that conceptual information motivationally significant (CS+). When each image appeared, participants rated whether they expected a shock on that trial, which provided a behavioral index of aversive learning. To examine how aversive learning influenced post-encoding hippocampal resting-state functional connectivity, resting-state scans were collected immediately before and after Phase 2 of the encoding task. Participants returned 24 hours later for a surprise recognition memory test (gray box). During this memory test, participants viewed all of the animals and tools they had seen during Phase 1 (blue borders) and Phase 2 (gold borders) of the experiment, along with new animal and tool ‘lure’ items (gray borders). Participants simply indicated whether each item had been seen previously (‘old’ judgement) or was completely new (‘new’ judgement). The critical measure in this study was the retroactive memory effect (RME), which was computed by subtracting participants’ corrected recognition memory for Phase 1 CS− items from their corrected recognition memory for Phase 1 CS+ items. Higher RME scores index a greater retroactive memory benefit for Phase 1 items that are conceptually-related to the aversive (CS+) category from Phase 2. Lightning bolt indicates shock.