The Divided Brain and The Asymmetric Body
Embodied and Dissociative Experiences Explored
In this article, I seek to coherently bring together three of the major themes which run through and inform my writings, and explain how these all fit together, and what this tells us about the human condition. The three parts/themes are:
the “Divided Brain” research of Dr Iain McGilchrist, on how the left and right hemispheres of our brains provide us with two very different ways of attending to the world, and two very different experiences of our own bodies;
the right hemisphere “Cortical Shock” model of chronic illnesses and trauma of Dr Joaquin Farias and Bonnie Badenoch, which suggests that, under conditions of chronic stress, our right brain cortex gets shutdown, and that this manifests as asymmetric physical symptoms in our bodies;
the Vagus Nerve research of Dr Stephen Porges, which states that we have left and right branches of this major bidirectional super-information highway between our brain and body, and that these left and right Vagus Nerve branches have markedly different motor and sensory functions in the body.
The Divided Brain
We begin with the research of Dr Iain McGilchrist, on the different ways that the left and right hemispheres of our brains work. For anyone unfamiliar with his work, I highly recommend the short RSA Animation. An interesting and relevant side note here from the video is that, as well as being functionally totally asymmetric, our brains are physically highly asymmetric too!
Let us begin with some quotes from McGilchrist’s book “The Master and His Emissary”.
“The right brain hemisphere is deeply connected to the self as 'embodied'. The left carries an image of only the contralateral right side of the body - when the right hemisphere is incapacitated, the left side of the body virtually ceases to exist for that person! The right lobe, however, has a whole body image, disturbances to this lobe lead to profound illnesses, such as body dysmorphia and anorexia nervosa.”
“The right and left also see the body in different ways... the right is responsible for our sense of body as something in which we 'live'... for the left, the body is something from which we are relatively detached, a thing, devitalized. There is greater proprioceptive awareness in the right, where it is far more closely linked to physiological changes that occur in the body when we experience emotions.”
Proprioception is the sense of location and movement of our own body parts.
McGilchrist provides illustrative case studies revealing just how deep and profound right hemisphere damage goes:
“the left appears to see the body as an assemblage of parts... if the right is not functioning properly, e.g after a right hemisphere stroke, the left may actually deny having anything to do with a body part which does not seem to be working according to the left's instructions... One person believed quite firmly that the paralysed arm belonged to her mother!”
I often use this example to illustrate just how profoundly delusional we can be when we are stuck in left-hemisphere overactivated states.
Another important point for later is that, according to McGilchrist, the right hemisphere is also mainly responsible for our “social engagement functions”, including “prosody” of voice [the melodic, emotional content of speech], and facial expression. According to McGilchrist, not only do these tend to go offline with right hemisphere damage, so does the ability to recognize emotions in the faces and voices of others.
The Asymmetric Body
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While McGilchrist’s work is illustrated by what happens to folks who have lost functionality of the right hemisphere due to physical damage, e.g. from a stroke, the research of Dr Joaquin Farias and Bonnie Badenoch reveals that the right brain hemisphere can go in to [emotional] “shock”, e.g. due to a chronic illness, or trauma. Basically, even though there is no physical damage, our right hemispheres can get temporarily shutdown when under chronic stress or duress, with similar outcomes as if we had had a right hemisphere stroke!
According to Farias, dystonia, abnormal muscle tensions, chronic pain, and movement disorders result from the brain forgetting or losing sight of specific muscles, typically on the left side, and thus muscles on the opposite side (usually the right) over-compensate, thus becoming permanently cramped and chronically painful, all caused by right hemisphere going into cortical shock. This concurs with McGilchrist’s perspective that, when the right hemisphere is not functioning, the brain loses the sense of half the body.
This led me to wondering whether internal organs could also be affected, as well as the muscles. Indeed, does a right cortical shock due to chronic stress also mean we lose some of our internal senses of our bodily functions - our “interoception”, as well as our proprioception? If indeed "when the right hemisphere is incapacitated, the left side of the body virtually ceases to exist for that person" what does this mean for the feedback and proper working of the parts inside our body on the left?
I think this is a very interesting idea to consider, since our internal workings are far from symmetrical, as shown in the image below from wikipedia. So if we now consider a right cortical shock, which internal parts to left might also be forgotten?
The most notable organ highly orientated to the left is the spleen. The spleen is crucial for proper immune function, infection control and the lymph system. Auto-immune type symptoms, poor response to infections, and inflammatory issues abound in those of us with trauma issues, chronic conditions, and when we are under chronic stress, indicating that indeed poor spleen function could be at play.
Note the heart does not lie symmetrically across the bodies centre line, either. Could a right cortical shock go hand in hand with poor heart rate variability (HRV), which is associated with a weakened response to external and internal stressors? Again, HRV tends to be notably downregulated when we are suffering from chronic conditions. We will explore, and provide some answers to, this question, more below.
The shape of the stomach and the intestines are also highly asymmetrical, e.g. the ascending colon and the descending colon are on opposites sides. Would my idea therefore help make sense of why those of us suffering trauma and chronic conditions tend to have very significant issues with digestion, food sensitivities, irritable bowel type disorders, constipation, etc.?
Below are some notes from the very interesting scientific article “Vagal Tone and the Physiological Regulation of Emotion” by Dr Stephen Porges, and co-workers. Indeed, I found this particularly interesting because it appears to provide the physiological link between McGilchrist's divided brain research, which looks at the different functions of the left and right hemisphere's of the brain, and Farias' cortical shock model, which explains movement disorders and dysautonomia as originating from the right hemisphere going into shutdown due to an [emotional] shock.
“The Vagus Nerve is bilateral, with a Left and a Right branch. Each branch has two source nuclei (dorsal and ventral) where the nerve fibres originate in [the brainstem]”
So as well as Dorsal and Ventral Vagus Nerves branches, there are Left and Right branches of both as well, which run down either sides of our necks and then wander off to various organs.
“Pathways from the Left and Right Dorsal Vagus Nerve to the stomach have different regulatory functions. The Left Dorsal Vagus innervates the cardiac and body portions of the stomach that promote primarily secretion of gastric fluids.”
So here is a first illustration that the functions of the left and right branches of the Vagus Nerve are asymmetric in function.
“The Right Dorsal Vagus innervates the lower portion of the stomach that controls the pyloric sphincter regulating the emptying into the duodenum [allowing emptying of the stomach into the small intestine].”
So the left and right branches of the Dorsal Vagus are both intimately involved in the gut, but do different things there. Dysregulation of the Right Dorsal Vagus, e.g. due to damage to the right side of the brain, will have specific impacts on digestion.
“The Ventral Vagus is also lateralized. Whie the Right one provides the primary input to the sino-atrial (S-A) node [a group of cells located in the wall of the right atrium of the heart, which spontaneously produce an electrical impulse, that travels through the heart, causing it to contract, setting the rhythm of the heart] to regulate atrial rate and determine heart rate, the Left one provides the primary input to the atrio-ventricular (A-V) node [co-ordinates the top of the heart] to regulate ventricular rate."
So both the Left and Right Ventral Vagus Nerve branches are involved with the heart, but again they have different, asymmetric functions.
“...characteristics of right-side brain damage are associated with defective Right Ventral Vagus regulation. In this manner, the observed deficits in prosody [melodic tone of voice] and in heart-rate changes… associated with right-side brain damage… implicate the Right Ventral Vagus in the regulation of vocal intonation and attention.”
Indeed, so this provides the physical link between McGilchrist's divided brain research and Farias's "right cortical shock" model of dystonia and dysautomnia: during a right hemisphere cortical shock, the Right Ventral Vagus will also be downregulated and partially offline, resulting in the loss of control of the motor and organ functions that it is primarily responsible for.
The right brain hemisphere is ascendant in our embodied experience, and in emotional and social engagement with our fellow humans.
When the right hemisphere is damaged, we become dissociated from our body, and emotionally disconnected from other people.
The loss of control of the Right Vagus Nerve due to right hemisphere damage can result in disruptions of physiological function, including facial expression, tone of voice, digestion and cardiovascular regulation.
When we are under chronic stress, or suffering from chronic illness or trauma, the right hemisphere can go into shock or shutdown, and hence the same presentations as physical right hemisphere damage can manifest temporarily, including the disconnection from our own body and from other people, and the loss of control of heart, face, voice and digestive functions.
One of the major pragmatic reasons for sharing this information is to help us all to be more understanding and forgiving of how the people in our lives are affected by chronic conditions, stress and trauma. Hopefully, this knowledge allows us to have more compassion when others necessarily disconnect from us, or behave in seemingly hurtful ways, due solely to involuntary physiological shifts that occur when they are under stress and duress. Furthermore, it instructive that, if we wish to help, we need to engage folks who are suffering in ways which will activate and stimulate their right hemispheres, and Vagus Nerves, and to avoid causing these to shutdown even harder. In other words, I hope it reveals something important about the human condition.
Moving on to how this information helps us to help ourselves. Firstly, it allows us to recognize when we are stressed, or not in a healthy state, ourselves, based on how disconnected or dissociated we are from our own body and how disconnected we are feeling from people in our lives. Secondly, it allows us to recognize that chronic stress is a root cause of many physiological symptoms, and that stress reduction and trauma healing is therefore key and vital to physical symptom reduction.
It also informs us that we can benefit through practices which activate and strengthen the right hemisphere and the Vagus Nerve, so as to build resilience against them shutting down. These systems tend to atrophy with lack of use, and hence one can get in to viscous circles of them become weaker and shutting off more easily, so it is vital to exercise to them. Dancing and tai chi are particularly beneficial for increasing proprioception and interception. Singing is particularly beneficial for exercising the social engagement circuits.
Basically, we need to engage in “neural exercises”, and also make changes in our lives, which activate and bolster the right hemisphere’s way of attending to the world. Similarly, engaging in practices which increase “Vagal Tone”, as measured through heart rate variability, through Vagus Nerve stimulating activities, will also help.
For example, Dr Farias has created a “Dystonia Recovery Programme”, where he offers a wide variety of neural exercises based on these concepts. I also keep and provide a master list of suggestions of things we can do to improve matters here: