Schematic illustration of the experimental procedure (A) and stimulus presentation (B).

<p>Emotional and neutral pictures were randomly presented in a continuous picture stream (each 4 s). Participants were verbally instructed that the colored picture frames (blue or green) indicated either threat-of-shock or safety periods. Abbreviations P, N, U refer to pleasant, neutral, and unpleasant picture contents; I refers to instructions slides announcing “Shock possible” or “No shock” preceding each 72-s period of threat-of-shock or safety.