While writing on the still unfinished paper mentioned in my first post I stumbled upon this figure from one of my previous papers and thought it might be a good idea to share it with you. Thanks to open access publishing I am actually allowed to do that.
The figure shows how complex sensations that people have during laser acupuncture follow the courses of classical channels of Chinese medicine (aka. meridians). Such sensations were mostly described as “tingling”, “warm”, “radiating”, and “spreading” by the participants and are probably related or identical to the so-called Deqi sensation often observed in needle acupuncture.
The results of this study are entirely based on drawings that participants made directly after being stimulated at the point marked by the arrowhead. To be able to compare the drawings from different people we gave them a body outline to draw on. The drawings were then digitized and analyzed by my co-author, Irene Marzolff.
On the left side of each image you see the raw results. The darker the gray is the more subjects reported sensations in that area. Notice how wide-spread sensations were. I remember this being puzzling to some of the participants. The person with the sensations up to the cheek and temple was a fellow neuroscientist from Frankfurt University. I still remember his face when he described his sensations to me. He was flabbergasted because he could not believe that a weak laser of only 20mW could cause this. I wonder how he would have looked if I had told him that his brain probably just made the whole thing up. But that is something for a future post…
While the left side includes all sensations, the red lines in the center of each image represent only the line-like sensations drawn by the participants (they were allowed to draw points, lines, and areas). Thanks to the software that Irene used, we were able to calculate the average course of the sensations (green lines) and compare it to that of the channel.
As the course of channels tends to vary between different literature sources we included four different versions of each channel in our analysis. Two were based on atlases (“Deadman” and “Porkert”), the other two on drawings from highly experienced practitioners. The variability can best be seen for the course of the SI channel on the shoulder blade.
When we calculated the mean distance between sensations and channels we noticed that it was in the same range as the variability of the channel course. Now, what does that mean? It means that the sensations could not have followed the channels more closely. So there are sensations triggered by stimulation of certain points on the body that spread or radiate from the stimulation site following lines that Chinese medicine has known for centuries. This is definitely one of my favorite discoveries as it gives us an idea, why people invented something so complicated as channel theory.
Imagine you are an ancient doctor and since you lack an ECG and X-ray you actually have to listen to your patients or even touch them (attention, irony). Every now and then someone comes to your practice telling you about a weird radiating sensation that he or she had experienced. If you as a doctor are trying to increase your knowledge of the human body, maybe this would make you think, what could cause such sensations. And maybe, because it fits into the cultural background of that time, you would start to think about structures, like channels.
Today, there is still nothing in Western physiology or anatomy that could explain the channels of Chinese medicine. So the connection that Irene and I found may actually shed some light on this concept that is otherwise frequently ridiculed and used as an argument, why acupuncture is pseudo-science. Well, maybe it is not…
Of course Irene and I were not the first to notice a similarity between acupuncture sensations and channels. Much research of this kind has been conducted in China in the 70s. The phenomenon was called propagated sensation along channels. Unfortunately, almost none of the results are available in English as this was the time before China opened itself to the West.
For those of you with a neuro background: Does anyone know, what could cause line-like sensations like this? Of course I know of dermatomes, referred pain and the like. But except from shooting radicular pain I know no sensation that follows a line on the body.