In the modern society, the drug addiction causes the social problems. Once people addicted, they

are easily fail to resist one’s desire to obtain and take drugs despite it has a negative outputs

(Volkow and Li, 2004). Resting state functional networks of the human brain can be investigated by

analyzing the correlation over the whole brain. The reward system involving the nucleus accumbens

(NAcc) is one of the main regions related to drug addiction (Baler and Volkow, 2006). In this study,

therefore, we investigated whether there is a difference of functional connectivity started from NAcc

between drug users and normal subjects.