Expectations modulate long-term heat pain habituation.

Habituation to pain was shown to be a complex mechanism involving the pain encoding regions and the antinociceptive system in the brain. Pain perception can be modulated by cognitive factors; however it is unclear whether cognitive factors also influence habituation to pain. We used an established experimental design with repetitive moderate painful heat stimulation over eight consecutive days. Thirty-seven healthy subjects were recruited and assigned to four different groups: The first group (n=10) was instructed that pain perception over time will habituate; the second group (n=9) that pain will increase; the third group (n=8) was instructed that pain will remain stable over the 8 days of…