There are several brain areas responsible for neuropathic pain reported in functional image studies, including primary sensory cortex, insula, and anterior cingulate gyrus. However, it is few informations about the functional status of these areas. Besides, the reason of the individual variability about the developement of neuropathic pain remains unknown. It is lack of satisfactory explanation about why some people developed neuropathic pain in certain diseased situation (for example, type 2 diabetes), while others do not.