in participants as they rated the pain of a hot stimulus applied to their arm.
The Placebo Effect
The participants were conditioned to think of three types of cream to have been applied to their arms. They are – a pain-relieving cream with lidocaine, a heat-intensifying cream with capsaicin, and Vaseline.
However, in reality, all three creams were Vaseline, and any perceived differences in pain came from the placebo or nocebo effect (imagined increases in pain).
The activity in the same brainstem circuit was influenced by placebo and nocebo effects but in opposite ways.
The strength of the placebo effect was linked to increased activity in an area called the rostral ventromedial medulla and decreased activity in a nucleus called the periaqueductal gray; the nocebo effect induced the opposite change.
Hence, these results reveal the role of the brainstem in pain modulation and may offer a route for future treatments of chronic pain.
Source: Medindia
