Pain is inherently unpleasant and has the characteristic of protecting the body by promoting motivation and learning.Relief from aversion(including pain relief)is rewarding.The aversion to pain and reward from pain relief are encoded by brain mesocorticolimbic circuits characterized by reward/motivation.This paper reviews the research findings about the effect of pain and acupuncture on reward/motivation circuits derived from animal models and human neuroimaging.It is further suggested that neuroimaging techniques may be used to track brain regions that mediate acupuncture effect

and the response of reward/motivation circuits to acupuncture could be used as an objective indicator of analgesic efficacy.It may provide help for further study on the brain mechanism of acupuncture in improving chronic pain.