Now, let's go a bit deeper into the neurology without leaving the forest behind, because this forest is inside you, and because the way that the nervous system is understood in mainstream allopathic medicine has denatured a number of fundamental understandings that we will require if we are truly to make sense of ourselves, to understand who we are, and what we are doing here. And this is, of course, as I have already noted, because the study of neurology, the study of much of anatomy, has been done through the dissection of cadavers. Dead people. People devoid of the animating spark, breath, pulsation, rhythm, and movement. Bodies more different from living people than the Oak in winter from the Oak in summer.
FROM SOMEWHERE TO SOMEWHERE
I have studied neuroscience for more than 30 years. I have studied with some of the world's leading neurophysiologists, psychophysiologists, neurobiologists, and emotion researchers. And in 30 years of study I have never heard someone point out that neurons grow from somewhere, toward somewhere. Like a tree seeking light, a neuron, when it develops, grows from a source in a direction. Most of what we are looking at, as clinicians, as wellness professionals, are nerves already formed. But in the process of becoming that way, they are growing, and they grow from somewhere to somewhere. Because we are neuroplastic, ever-changing neurologically, our nervous systems are constantly growing and pruning connections. Our neurobiology is a use it or lose it proposition. Embryonic development, and infant development more broadly, is accompanied by explosive neural development.
Various parts of us fold inward on themselves, the outside becomes the inside like dough rolled and folded on itself, and then parts of us migrate, move, shift into position. It is appropriate here to visualize timelapse photos of plants growing in the spring, of roots deepening into soil substrate. Neurons bring their own blood supply, so that the circulatory system grows in tandem with your neurology. There is massive neural growth, and then myelination. Myelin, the fatty sheath that grows around neurons rather like insulation around a wire, increases the velocity and precision of signal transmission. Our earliest development is characterized by massive neural and vascular growth, the inward forest branching and finding itself, then the insulation of circuits that are being used, followed by subsequent pruning. The tree grows toward the light. If there is no light the limbs die back. This happens again and again and again. A five-year old learning to hold a pencil in her right hand is generating new neurology.
ATTENTION IS THE LIGHT
A beautiful secret: Attention is the inward light. At forty-five when you learn a new language, you are generating new neurology. The algebra you've forgotten as an adult? Pruned because you didn't use it. Attention is the light. Pass attention over the neurology to keep it alive. Attention is the inward sun passing across your aboriginal neural forest.
In the inward forest attention is the light.
A REVISED MODEL OF THE AUTONOMIC NERVOUS SYSTEM
Orthodoxy in neuroscience states that the Autonomic Nervous System (ANS) originates in the brainstem. This ANS circuitry is distinguished from midbrain circuits that are involved with emotion and emotion regulation, and cortical circuits involved with language and abstract thought. The brain, we learn, develops from the bottom to the top, from the back to the front. The autonomic circuitry, which regulates our internal milieu, begins in the basement of the brain, and is then the neural foundation beneath our emotions and cognition. Or so we are told. The problem is that this is not true. What I am about to explain to you upends several hundred years of orthodox neurology, but the logic of this proposition is very straightforward.
Most of your autonomic circuitry does not begin in the brainstem for the simple reason that neurons grow from somewhere, to somewhere. If you want to understand where neurons start, you look at the direction of information flow, because neurons can only send a signal in one direction. Allow me to be more precise in how I say this: if you want to know where a neuron started, and where it ends, where it grows from, and where it grows to, look at the direction of information flow. From where is it receiving information, and to where is it transmitting information. Do you understand what I am saying?
In our brain-centric model of neurology we classify nerves as either afferent (upward flowing from the body toward the brain) or efferent (downward flowing from the brain to the body). What I am saying is very simple: if a nerve is afferent, it doesn’t begin in the brain. It ends in the brain. This is why the ANS cannot begin in the brainstem. The Vagus is 70-80% afferent.
70 to 80% afferent means that 4 out of 5 fibers are flowing upward into the brain. If they are flowing upward into the brain they did not start in the brain. This afferent Vagus doesn’t begin in the brainstem. It ends in the brainstem. The sources of the sensory afferents of the ventral vagal system are not in the brainstem. The terminations of the sensory afferents of the vagal system are in the brainstem. The afferent Vagus (which is most of the vagal system) begins in the guts (and the soles of the feet, the palms of the hands, the skin, the visceral organs, everywhere in your body), and then unites in the heart.1 From the heart it makes its way up into your brain.
What I have been presenting to you, so far, is a revised model of neural development that is not brain-centric, because my contention is that this brain-centric model is the accidental and delusional byproduct of a worldview over-identifying self with thinking (I think therefore I am.) Thinking (in words and pictures) happens locally in the head. If you identify self with thinking (axiom Descartes), you elevate the organ where this thinking happens in your construction of intelligence and you center it in your neurology.2
If we understand neural systems, and we understand how they grow, we are forced to come to the conclusion that direction of information flow in a neural conduit corresponds with how the conduit developed. When we say that that Vagus is 70-80% afferent, i.e., flowing from the body upward to the brainstem, the corollary to this awareness is that it is 20-30% efferent, flowing downward from the brainstem to the body.
In order to understand this more deeply, and more systemically, in ways that have profound implications for understanding who we are, and how our nervous systems (and therefore our bodies) work, we have to deep-dive into a particular niche of neuro-embryology that studies the earliest development of the nervous system, at the stage of feotal development when your spinal cord and brain are forming. This is, once again, specialist knowledge that you need to understand, because its practical implications for your life are enormous.
NEUROEMBRYOLOGY
We are looking at the developing fetus (you) at the moment when it begins to fold in on itself and invaginate (the technical term). This is within the first few weeks of embryonic formation, within 14-17 days of conception. At this moment, the outer layer of the embryo gets folded inward on itself (imagine a baker rolling out a sheet of dough, gathering both edges and folding them back the center, and then rolling it again. Did you realize you were a neural croissant?). This outer become inner will become your spinal cord and brain. And between them a cell layer called mesoderm will develop into your vascular system, heart, and blood. At this moment, the heart has already started to beat, but it is not in the place it ends up in. At this moment of very early embryonic development, your heart is above your head.3
I’m going to say that once again, because it is so deeply strange. At the moment when your spinal cord and brain form, your heart is above, north of, your body. It is on top of your heard: north of the cranial end. The heart then begins to migrate downward, south, in the direction of your feet, until it eventually reaches your chest, which is where it will end up. Amazingly, the chemical that ignites this migration comes from what will become your guts (your endoderm, in the form of a growth factor called VEGF - vascular enthothelial growth factors). The heart begins to migrate south, along the ventral surface of your brain, catching it neurally on the way down. I want you to try to visualize this, because it is important. Your heart has its own intrinsic nervous system. It is also, as it migrates southward across the ventral face of your brain, sending out dendrites that link into the brainstem. At this moment, it is like a plant sending tiny shoots that root into the brainstem. The brain in turn reaches back.
What I just said, and what you have just understood, is that at the earliest stages of your neural development, your heart migrates from north of your head, slides down the front side of your brain, and catches your brainstem as it passes. Strange, no? This neural link-up between heart and brain becomes your Vagus. Four out of five of its fibers are running from the heart to the brain, the fifth is running from the brain to your heart. If this is a highway, it has four lanes running from heart to brain, and one lane running from brain to heart. In other words, it is highly asymmetrical in terms of information flow, favoring pathways from body to brain over pathways from brain to body.
Under a specific range of conditions, and these are the conditions that your physiology is optimized to reside in, the ancestral conditions this book will teach you how to inhabit, this foundational wiring integrates inputs from the whole body in the heart, and then passes them up into the brainstem, giving your heart sovereign control over your brain. You have four lanes of control running up from the heart to the brain. This system, the foundation of your neurological connection system, is capable of organizing and harmonizing all the afferent inputs from your body with an extraordinary degree of refinement. Yet, also, in the conduit of this connection, there is, in parallel, a single lane running down from the brain to the heart. This lane permits the brain, under certain conditions, to control the heart. But this neural control is less robust, precise, graded. It is less capable of entraining all of your other organ systems.
And do you know when that system activates?
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