Fig. 2. Placebo-induced changes in regional cerebral blood flow (rCBF). (  A ) Placebo-related decreases in rCBF in medial thalamus, rostral anterior cingulate cortex, and nucleus accumbens. (  B ) Thalamic blood flow changes (  red dots ; centered adjusted rCBF) and changes in pain ratings (  green values ; scores on 10) over the course of the study. Thalamic activity decreased gradually between scans 5 and 9,  i.e. , the period of stepwise titration of the placebo response (the  arrow indicates injection of epidural “opioids”). The patient was pain free during scans 9–12. Before the last three scans, a nocebo suggestion was given (the  arrow indicates injection of intravenous “opioid antagonist”), which resulted in a prompt increase in pain ratings and a concomitant increase in thalamic activity.