ROIs analysis results of the four overlapped areas between the activated areas in the first block and the habituated areas in the course of repeated acupuncture stimulation.

The brain responses to acupuncture stimulation were increasingly decreased as the acupuncture cumulative duration became longer. The characteristic of habitation was bimodal, i.e. positive brain response was found in the first block of acupuncture stimulation, then it began to decrease and brain response became negative in the last (R: Pearson’s correlation coefficient).