This study looks at fMRI in 5 subjects during heat pain, and then with Optimal electroacupuncture and Minimal electroacupuncture.  Both types of acupuncture suppressed the brain activation from heat pain, but the optimal electroacupuncture more so. They used 5Hz electroacupuncture which is a somewhat unconventional choice, since most studies look at either 2Hz or 100Hz.
This type of suppression could be of great clinical value in cases of chronic pain, since one school of thought is that the brain recruits more and more “real estate” the longer it goes on.  So if you can suppress those inputs, perhaps the vexing chronic pain pattern may diminish. Full article at the link.  (For more information about my practice, please click here.)

Shivshil Shukla,1 Artour Torossian,2 Jeng-Ren Duann,3 and Albert Leungcorresponding author4

Received December 8, 2010; Accepted June 7, 2011.
Electrical acupuncture (EA) has been utilized in acute pain management. However, the neuronal mechanisms that lead to the analgesic effect are still not well defined. The current study assessed the intensity
[optimal EA (OI-EA) vs. minimal EA (MI-EA)] effect of non-noxious EA on supraspinal regions related to noxious heat pain (HP) stimulation utilizing an EA treatment protocol for acute pain and functional magnetic resonance imaging (fMRI) with correlation in behavioral changes. Subjects underwent five fMRI scanning paradigms: one with heat pain (HP), two with OI-EA and MI-EA, and two with OI-EA and HP, and MI-EA and HP.
While HP resulted in activations (excitatory effect) in supraspinal areas known for pain processing and perception, EA paradigms primarily resulted in deactivations (suppressive effect) in most of these corresponding areas. In addition, OI-EA resulted in a more robust supraspinal sedative effect in comparison to MI-EA. As a result, OI-EA is more effective than MI-EA in suppressing the excitatory effect of HP in supraspinal areas related to both pain processing and perception.
Intensities of EA plays an important role in modulating central pain perception.