The first documentation that clearly describes the meridians was the The Yellow Emperor’s Classic of Internal Medicine, dating from about 100 BCE. There are 12 major meridians and 2 midline meridians. The 12 major meridians are further divided into 6 yang (downward flowing) and 6 yin (upward flowing) meridians that are paired based on whether the associated organs are considered 'hollow' or 'solid'. This pairing creates a looping, longitudinal circuit that is continuously flowing Chi up and down the body. These meridians have superficial aspects that allow them to be needled (acupoints) and deep pathways that run through the tissues and organs they’re named after.

In the early 1960s, a Korean researcher by the name of Bong-Han Kim proposed a system he called the Bonghan Ducts as the physical basis for the Chinese Meridian System. His work was largely passed over until in 2002 at the Seoul National University a team of researchers led by Professor Kwang-Sup Soh investigated further and conclusively confirmed that this system represented the physical construct of the acupuncture system. They renamed it the Primo Vascular system and have shown it exists in the same locations as the traditional meridian system acting as a third circulatory system after the cardiovascular and lymphatic systems. These "Primo vessels have bioelectrical activity, excitatory conductivity, and mechanical motility", Stefanov et el.

Here’s a great video from some researchers on how to identify the PVS using a staining dye injected into the body. In their example, they chose to look at a section of PVS inside of a Lymph vessel because the normally transparent tissue will clearly elucidate with the dye. The width of these tubes is 20-30 micrometers; contrast that with the thickness of human hair 60-120 micrometers. Thornton Streeter, a biofield scientist and recent guest on the podcast, has put together this lovely presentation on the PVS and its relations to both TCM and the Nadis of the Yogic/Ayurvedic traditions. https://www.slideshare.net/thorntonstreeter/primo-vascularmeridian-system-2016

Another previous guest, Rajan Narayanan, used this system as the basis for his study published in the International Journal of Yoga 2018. https://www.ncbi.nlm.nih.gov/pubmed/29755226 It seems the PVS ties together the endocrine, lymphatic, cardiovascular and nervous systems in an electromagnetic biomatrix that can be measured with Electro-Photonic Imaging. With this integrated perspective, Narayanan was able to use Pranayama (breath work), among other yogic techniques, as a successful and precise intervention for numerous patients.

Four meridians are known to travel to the brain including the Stomach/Spleen circuit which pass through the frontal lobes and the Liver/Gallbladder which flow through the brainstem and Limbic lobes (emotional centers). In particular, the liver meridian "connects to the hypothalamus, reticular structure, limbic system, eyes, visual pathways, proprioceptive pathways, vestibular system, cochlear and auditory pathways, and motor conduction pathways", Lui et al. 

I recently came across some work at a joint Havard-MIT Bioemedical imaging center that used fMRI to see changes in the brain as a result of needling acupoints on various meridians in the body. Incredibly, they were able to show deactivation of the Limbic brain and Amygdala through needling the acupoints Large Intestine 4, Liver 3 and Stomach 36. In addition, this had an effect on deactivating the Default Mode Network, which is the same network affected in meditation.

An amazing correlation exists here in which LI4 and LV3 in TCM constitute the Four Gates. The Four Gates are reknown in acupuncture for creating physiological, homeostatic balance and a very relaxing, peaceful state. 

And just in case you're interested in researching this topic further, here's another acupoint/fMRI study: The human brain response to acupuncture on same-meridian acupoints: evidence from an fMRI study.

Dawson Church, a previous guest on my podcast recently released a book called "Mind to Matter". I’m loving this book right now and his case for the primacy of consciousness and its shaping of reality. For those of you not up on this centuries-old debate, essentially the arguments are one camp, the materialists, contending that consciousness/awareness is an epiphenomenon of matter. The opposite viewpoint made by post-materialists/spiritual traditions/pre-decartes humans is that consciousness is the foundation of and source of matter. For those interested in learning more on the later, you can explore the work of Dean Radin and IONS. 

Back to Dawson's book.... he reports an anecdotal study performed by Australian journalist, Graham Phillips, and Graham’s personal investigation into Mindfulness meditation’s effects on his brain. You can view the 30-minute tv report here.

Graham hooked up with a research team at Monash University to obtain baseline values for standard behavioral and neurological tests including MRI. After 2 months, one of the most significant changes was Graham’s increased performance in cognition - decreased distractibility, increased reaction time and increased working memory. At the same time, he had a simultaneous decrease in neural activity. So, what does this mean? Mind-Brain efficiency. Of course this is an objective measure. What’s most important is how someone feels after 2 months of Meditation - why else would you do it?! Graham reports not only feeling more at ease, but also noticing stress without becoming entangled with it. This is commonly reported over and over by practitioners with a regular meditation practice.

Default Mode Network (DMN)

In addition to increased performance, his MRI revealed a 22.8% increase in the grey matter of the Hippocampus. The grey matter is the nerve cell bodies and dendrites that communicate information electro-chemically. This neurogenesis in Graham's Hippocampus, the learning and memory area of the brain, allowed Graham a greater degree of control over his Default Mode Network (DMN). The DMN is a crucial network in the brain, and when overactive, pivotally involved in rumination, anxiety, storytelling and generalized anxiety. It is also positively affected by a meditation practice. 

Dr. Richard Chambers who consulted Graham in his 2-month journey says: “A paper that came out last year (2015), a meta-analysis, has found that it's as effective as antidepressants for preventing relapse, which is a pretty significant finding. Depressive thoughts that go through people's minds that they don't normally notice, they're just running in the background like an app and reducing people's mood. So mindfulness helps them to notice that and then just to recognize it as a thought rather than taking it seriously, believing it, trying to push it away, which then gets the attention very much caught up in that kind of rumination. Just noticing it, let it go, bring the attention back to the present. “

Another important effect of meditation is the reduction in stress hormones Adrenaline and Cortisol, both of which according to Dr. Elissa Epel Telomere researcher at UCSF, accelerate the aging process. As you can see, the mind is shaping our biology whether we aware of it or not and the salient point meditation makes is: stress is not the situation, it’s the way we relate to the situation.