Acupuncture provides a second noxious stimuli that inhibits pain from the original stimulus; in other words, pain inhibits pain. This is called conditioned pain modulation. Segmental pain inhibition is the term for the slow nerve fibers that, when activated by rubbing an injured area, inhibit pain transmission from a fast nerve fiber. Expectancy-related cortical activation and placebo effect are the same term to describe the measurable effects cognitive expectations can have to modulate pain perception.