Now, a growing body of research suggests that it may have several mechanisms of action. Those include stimulating blood flow and tissue repair at the needle sites and sending nerve signals to the brain that regulate the perception of pain and reboot the autonomic nervous system, which governs unconscious functions such as heart beat, respiration and digestion, according to Alejandro Elorriaga, director of the medical acupuncture program at McMaster University in Ontario, which teaches a contemporary version to physicians.

A specialized MRI scan shows the effects of acupuncture. The top two images show the brain of a healthy subject. In the middle two images, a patient with carpal tunnel syndrome registers pain (indicated by red and yellow). The bottom images show the calming effect (indicated by blue) in the brain after acupuncture.

"You can think Western, you can think Eastern. As long as your needle goes to the nerve, you will get some effect," Dr. Elorriaga says.
What's more, an odd phenomenon occurs when acupuncture needles are inserted into the body and rotated: Connective tissue wraps around them like spaghetti around a fork, according to ultrasound studies at the University of Vermont. Helene Langevin, research associate professor of neurology, says this action stretches cells in the connective tissue much like massage and yoga do, and may act like acupuncture meridians to send signals throughout the body. "That's what we're hoping to study next," she says.

Meanwhile, neuroimaging studies at the Martinos Center for Biomedical Imaging at Massachusetts General Hospital in Boston have shown that acupuncture affects a network of systems in the brain, including decreasing activity in the limbic system, the emotional part of the brain, and activating it in the parts of the brain that typically light up when the brain is at rest.

Other studies at the Martinos Center have shown that patients with carpal tunnel syndrome, a painful compression of nerves in the wrist, have heightened activity in parts of the brain that regulate sensation and fear, but after acupuncture, their brain patterns more closely resemble those of healthy subjects.

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