Acupuncture Mechanism Studied by MRI

Evidence from Neuroimaging Studies

In more recent years, brain imaging has been used to clarify the relationship between acupoints and the functions they represent. The practice way pioneered by Dr. Zhang-hee Cho, UC Irvine professor of radiological sciences.

Dr. Cho showed in a series of imaging experiments, published in 1998 in the proceedings of the national academics of sciences, that needling several acupoints for eye problems-located near the little toe-in a group of 12 volunteers increased activity in the visual cortex, the part of the brain governing vision.

Figure 8. Side-by-side comparison of 2 cortical activations seen at the mid-line sagittal view due to: (a) pain vs meridian acupuncture (LI 3) + pain stimulation and (b) pain vs sham acupuncture + pain stimulation, respectively. Decreases in activation of the 2 appear similar, suggesting that they are based on similar neural mechanisms.

Yet when Cho and his colleagues stimulated random points, located a few centimeters away from each point, no activity occurred in the visual cortex.

Dr. Randy Gollub, assistant director of psychiatric neuro-imaging at Massachusetts General Hospital, is also investigating the differences in brain activity generated by needling at real and fake acupoints. In an ongoing study, healthy volunteers are subjected to pain and then given either real or sham acupuncture. So far, both treatments appear to activate or deactivate various regions of the brain involved in controlling the body’s reaction to pain: “they’re a lot more alike than they are different,” Gollub says.

But, she adds, it looks as if the brain’s response is stronger for true acupoints than for sham ones. “think of it as a mountain range, with the acupuncture points as peaks,” “as long as you’re not in the valley, the acupuncture is probably going to have some effect.”

Dr. Cho, for one, has found in recent studies that inserting needles in real or sham sites produces similar changes in parts of the brain perceiving pain.

In simplified terms, he thinks that inserting a needle at almost any point on the body triggers a series of biochemical messages between the brain’s hypothalamus and the hormone-producing pituitary and adrenal glands. The signals tell the body to alter its production of, for example, certain stress with stressors-such as bacteria, viruses, emotional trauma or pain.

In fact, Dr. Cho believes that acupuncture might someday be refined to the point where the use of a dozen or more needles could be traded in for a single well-placed needle. “one good stimulation may be enough” for lasting pain relief, he says.

Gate-control Theory of Pain

The “gate control theory of pain” proposed that pain perception is not simply a direct result of activating pain fibers, but modulated by interplay between excitation and inhibition of the pain pathways. According to the theory, the “gating of pain” is controlled by the inhibitory action on the pain pathways. That is, the perception of pain can be altered (gated on or off) by a number of means physiologically, psychologically and pharmacologically. The gate-control theory was developed in neuroscience independent of acupuncture, which later was proposed as a mechanism to account for the hypothesized analgesic action of acupuncture in the brainstem reticular formation in 1976.

This leads to the theory of central control of pain gating, i.e., pain blockade at the brain (i.e., central to the brain rather than at the spinal cord or periphery) via the release of endogenous opioid (natural pain killers in the brain) neurohormones, such as endorphins and enkephalins (naturally occurring morphines).

Acupuncture MRI (link: