Figure 1
Task Structure. (a) Participants were pre-familiarized to 115 unique images (75 outdoor scenes as illustrated and 40 faces) before each of the two scanning sessions that were completed 2–3 h after blindly administered typhoid vaccination and saline (placebo) injection. (b) Each scanning session consisted of two separate counterbalanced scanning runs. On one run, participants were shown a single target scene (illustrated on left) followed by randomly presented familiar, target, or novel scenes. Forty-two percent of trials consisted of novel, 42% familiar, and 16% target images. Participants made a speeded button press to each presentation of the target stimulus. The second run was identical to the first except that participants were shown target, novel, and familiar face images. Stimuli were presented for 0.5 s with a jittered (mean 3.4 s) intertrial interval.
