Following consent, subjects completed the Brief Pain Inventory (BPI), and Current Opioid Misuse Measure (COMM). Next, a temperature that corresponded to a 7/10 (‘intense, but tolerable pain’) on self-reported pain intensity was found for each participant. This temperature was used during the functional imaging session. The baseline for all subjects was identical: 32°C. Temperature events during functional imaging had a duration of 14 seconds. Each of the three sessions of thermal stimulation lasted 4 minutes, 28 seconds. There were 8 thermal events per session, for a total of 24 thermal events.