A Neuroplastic Theory for Distal Points

Another quick ramble based on some recent reading material…

Lately I have delved into Norman Doidge’s The Brain That Changes Itself. This was the book that launched neuroplasticity into the popular arena and while I have read numerous academic articles and books on the subject I have somehow managed to leave that one on my shelf gathering dust so I decided to read through it before my life gets occupied with herbs full time. While he was explaining Hebbian conditioning (summarised by Carla Shatz as: “Neurons that fire together wire together”) it occurred to me that this principle could explain how we develop a number of distal points, that is points in acupuncture which are quite distant from the site of a problem. It is always a difficult one to explain to people why we are using a point in the hand or foot to affect the head or trunk.

An existing theory has stated that when a needle is stimulated and sensation radiates away from it, it is actually occurring in the brain spreading from the place where the point is represented to its neighbouring areas. This is proposed on the basis that no physical structure equating to the meridians has been found to explain how the patterns of radiation are felt. The second part of this theory suggests that if certain areas are close to each other in the brain, but distant in the body then this radiating sensation could spread to influence them too. The relationship of one area to another has been mapped as early as the 1940s by neurosurgeon Wilder Penfield in a series of experiments using electrical stimulation of the brain and reports of where people felt the sensation in their bodies.

corical-homunculusThe Cortical Homunculus of Wilder Penfiend showing the sensory map of our brain areas related to body parts.

The problem with this theory is that while it may explain how a point like Hegu LI-4, near the thumb, can affect the face, it becomes more of a problem when trying to explain how a point on the little finger side of the hand can affect the neck as Houxi SI-3 is often employed to do. If we start to consider that Hebbian conditioning should wire together the areas that frequently fire together then areas of our body which touch each other or move together a lot are likely to form closely connected maps in the brain. Even if not close in space then they should form tight links to each other. This made me wonder if it could explain a number of other distal points and it does seem to work for most of the major ones on the arm and several on the feet. It does not explain them all but then I do not believe that we need a single mechanism to explain the location of all acupoints, just a plausible mechanism for each one to understand and refine our practice with. If we can develop a testable hypothesis then so much the better.

The Meridians of the Arm
The first example is Hegu LI-4 that also works under the hard-wired homunculus model explained above. It is commonly used for problems of the face and head including headaches, sinus problems, dental pain and often in combination with Lieque Lu-7 for colds, blocked or runny nose, sore throat, stiff aching neck and similar symptoms. Yuji Lu-9 also has similar indications of heat signs in the lungs, nose and throat and is probably the same point internally as Hegu LI-4, just approaching from the other side of the thumb. All of these points have a tendency to send a sensation down into the forefinger and thumb which is the part of the hand that will most frequently touch our face. Imagine scratching your face, rubbing your eyes, pinching your nose and massaging your throat or jaw, the first finger to reach is the forefinger or thumb. It would make sense that if we are repeatedly touching ourself on the head and face with this part of our hand that the signals would be arriving in our brain at a similar time, reinforcing the connection between these two areas.

The next point I considered which does not fit into a simple structural explanation using the cortical homunculus is Houxi SI-3 on the blade of the hand, at the side of the little finger for neck and back pain. As the confluent point of the Du “Governor” channel it is a major point for all problems of the spine. Grip and rub the back of your neck for a minute and see which area of your hand comes into contact initially and predominantly and you will see it is on this ulnar side, where Houxi SI-3 is located, especially up near the occiput, at the base of the skull. The lower back can indeed be held by any part of the hand but it is again the little finger side that will be closest to the spine with the thumb facing outwards in most scenarios, regardless of whether we use the palm or dorsum.

The third area that ought to become closely mapped is the Hand Shaoyin and Jueyin meridians of the Heart and Pericardium, also known as the Chest Centre and Heart Protector. So the next experiment to try is to put your hand on your chest and notice which part you instinctively use. It is probably the palm, the exact location of where the Heart and Pericardium channels run. This is also the place we would hold our hand over our stomach if we felt nausea which happens to be a major indication of the Pericardium channel, especially Neiguan Pc-6. While this point is located on the wrist, the sensation when we trigger it is often one radiating or even shooting into the palm and middle finger.

That covers all the meridians of the hand except one, the San Jiao or Triple Heater. Probably the most difficult one to translate into English as it has no equivalent and is bound up with esoteric meditation traditions. Its internal functions in terms of acupuncture are largely to do with body temperature and immune function, lowering fever helping us to reject an infection. This one runs across the back of the hand, the part we use most for measuring if someone has a temperature.

The Meridians of the Legs
The legs have less to do with touch making the associations of distal points a little less obvious. An exception to this is the sole of the feet where touch is essential for balance but we rarely touch ourselves with our feet making the theory that they could become wired together through touch less valid for the legs. There may be something to say in relation to our ability to touch through the soles of our feet and the idea of reflexology zones but I have not really considered this in much detail. Instead the distal points of the legs are most likely to become conditioned with a different simultaneous firing, that of movement.

The distal points of the Foot Taiyang meridian Weizhong Bl-40 at the back of the knee, and Kunlun Bl-60 at the ankle, are indicated for lower back pain and strengthening the lumbar spine. The back of the legs, including the knees and ankles are all involved in our ability to stand up straight and move forward. It would make sense that the necessity of their firing together will cause them to be closely wired in the brain. The same logic can be applied to Taixi Kid-3 whose location is effectively the same as Kunlun Bl-60 except approaching from the other side of the ankle.

Much the same can be said for the Foot Taiyin and Yangming meridians of the Spleen and Stomach. These run across the front of the thighs and onto the abdomen, another set of muscle groups that fire together when we raise our legs to our chest. It is therefore perhaps not surprising to find that Xuehai Sp-10 on the lower thigh is indicated for menstruation cramps while Liangqiu St-34, indicated for acute Stomach problems, is located next to it on the opposite side of the knee.

A similar suggestion might be implied in the use of opposite needling, where a problem in the right is addressed by needling the same point on the left. I find this especially useful if there is a reason why we cannot approach the problem area directly (e.g. possible infection, paralysis or numbness making sensation impossible). This may work by the fact that we tend to use our arms and legs together, especially our legs. It makes sense that the maps in our brain that sense and control the two halves will be closely linked. Needling one side strongly enough may be able to make the sensation radiate into the map for the other side. I am not sure how much this applies for some of the other systems I have heard of, such as needling the shoulder to affect the opposite hip, or the wrist to affect the opposite ankle – my personal suspicion is that this works simply through a centralised endorphin release and we could pick any point anywhere for the same result – but where the locations are identical or closely related then it could be affecting the other side through a connection that mediates hips, knees or ankles on both sides.

Another distal point that we may find are connected through simultaneous firing is Taichong Liv-3. Indicated for dizziness, perceived as being like a wind stirring in the head, it is located on the top of the foot and piercing deeply enough that it often sends a sensation right through the sole. This may be tapping into the connection mentioned above, between our ability to feel through our feet and the information which we process from the balance centres in our inner ear and visual information from our eyes. All of these have to work in close coordination in order for us to make the fine adjustments necessary to stay upright. A strong stimulation of the foot that radiates far might have the ability to spread to the areas of our brain that deal with our balance too. This same connection might indicate why Guangming GB-37, on the outside of the calf, and Zulingqi GB-41, also on the foot, are indicated for problems of the eyes. It may be referring to this connection between vision the fine motor control of our legs and feet that keep us upright. It has certainly always been my impression that the indication implies functional eye problems such as brightening up after a long time reading or on a computer, or for vertigo type blurring and swimming vision, than for eye problems of a physical nature.

Exceptions and Conclusions
The other distal acupoints of the leg may not be explicable by this theory. I have struggled to find any paired movements or sensations that connect such major points as Quchi LI-11, Zusanli St-36, Yanglingquan GB-34, Yinlingquan SP-9, Sanyinjiao Sp-6 and Taibai SP-3 with their distal functions. There is certainly no reason to assume all points have identical mechanisms or arise in the same fashion although it could equally be my lack of imagination that I have not thought of a common sense or movement by which they might be reinforced with their distal effect. It has been a error repeated in most modern attempts to explain acupoints to assume that they must share a common feature that will elucidate them all when the original term simply meant a “cave” or depression where a needle could be inserted. The inventors never considered modern mechanics so there is no reason to assume they should all share the same mechanisms. This model does present a possible theory as to how many come into existence using the current knowledge of neurobiology and may also explain why there is some individual difference in location and response to certain points.