Furthermore, gender differences of the human brain are an important issue in neuroimaging studies. It has been identified that gender has significant influence on the regional neuronal activity [189, 190] and brain structure [191]. Race differences may lead to differences of brain function and structure. For example, it is reported that brain size varies by race [192]. In this study, we found that 14 studies (8.33%) described and restricted the race of the participants. Taking gender and race as covariates is needed when designing acupuncture-neuroimaging experiments.