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I was once bed bound with a long list of chronic illnesses and debilitating symptoms. And in the end, it wasn’t medicine or a protocol that healed me: it was harnessing the power of brain retraining, rewiring my limbic system, and coming out of deeply ingrained trauma and nervous system stress patterns. Now the latest science is proving the link between the brain and the immune system, via a network of nerve fibers that connects the brain with the body: the vagus nerve.

Chronic Lyme disease, mold toxicity, Chronic Fatigue Syndrome, dysautonomia, POTS… this was my reality for years, and the list of diagnoses and symptoms went on. I suffered for well over a decade with debilitating chronic infections and sensitivities that caused deep suffering.

When I was at my worst I had two small children who I could barely interact with and care for, instead spending most of my days lying in bed in a darkened room, needing as little stimulus as possible. And despite (although truly because of) having such little functionality, I was trying what felt like everything to get better. I consulted with countless doctors and explored various treatments… yet I found myself trapped in a relentless cycle of suffering.

It wasn’t until I delved deeper into the root cause of my health challenges that I discovered the true culprit: limbic system impairment.

Through brain retraining we can rewire the brain, turn off the alarm in the limbic system, and regulate our autonomic nervous system to come out of survival stress responses. When we do this, we are able to heal other systems in the body that are governed by the nervous system.

Contrary to the diagnoses I had received, such as Lyme disease and mold toxicity, I realized that my body’s inability to heal stemmed from a dysfunction in how my brain processed stress and trauma.

It sure didn’t come without resistance at first though. I didn’t believe that resolving my trauma had anything to do with my Lyme disease and other issues. In fact, when my therapist at the time said to me:

“Cathleen, I think 80% of your Lyme disease symptoms would go away if you would learn the tools of nervous system regulation.”

I was livid. I replied: “I think 80% of my nervous system symptoms are due to my Lyme disease!” 

Turns out, he was in fact correct

We can harness the power of our brains to fundamentally change our biology for the better.

The Science of Neuroplasticity

I had to convince myself of the science behind brain retraining, neuroplasticity and nervous system regulation before I allowed myself to implement any of the practices. My rational brain needed proof that the limbic system and autonomic nervous system function are the cornerstones of unlocking self-healing from real infections and all of my other issues, and I wasn’t just gaslighting myself with some kind of Pollyanna-esque fairy tale whilst my very real and very unbearable symptoms continued to set my body on fire.

I researched and learnt from a couple of brain rewiring programs out there, and slowly the pieces began to fit. This stuff made sound, logical sense, and I was prepared to give it a go.

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An infographic to show the before and after effects of brain retraining. Follow us on instagram @primaltrust_official for more posts like these!

Essentially, the body’s nervous system is intimately connected with the brain, and in particular, receives stress signals from a part of the brain called the limbic system. The autonomic nervous system, via the vagus nerve, regulates every system in the body. Chronic and unresolving illnesses, especially those such as Chronic Fatigue Syndrome/M.E., Long Covid, chronic Lyme disease, POTS, autoimmune, mold toxicity, CIRS, MCAS etc, are associated with overactivity in the limbic system of the brain, the center that is responsible for emotions, memory, and behavior, and thus dysregulation of the nervous system. As a result, the body can stay in a state of chronic stress, and the nervous system stays stuck, informing various other systems in the body that it is not safe and perpetuating chronic symptoms.

In order to self-heal, we must specifically target the limbic system of the brain to shift the biochemistry of the body and trigger relaxation in the nervous system, creating a rest and digest state of activity. We must wire in new neural pathways, instead of running the habitual neural pathways that keep firing off a stress response in our body, and triggering the same issues and symptoms.

The Brain-Immune Connection

What I love seeing now, years later, is how more and more science is revealing how brain retraining works. Not only that, but we are learning about even deeper connections, such as how the brain governs the immune system – scientists recently have identified specific brainstem neurons, including those in the vagus nerve, act as the master regulator for the body’s inflammatory response, offering insights into immune system control.

Check out this article to read more:


Research such as this provides some incredible weight behind why calming the areas of the brain that inform the body’s nervous system via the vagus nerve has a modulating effect on the immune system, and explains how retraining the brain and stimulating the vagus nerve sees people turning on their body’s self-healing mechanisms and reversing all sorts of chronic health issues.

How I Retrained My Brain

So I started to learn how to retrain my brain. I began with interrupting the patterns of thoughts that were creating a cocktail of stress chemistry in my body – sufferers of chronic illness will be well aware of how the rumination goes – thinking over and over about symptoms, about how you are feeling, how much you want to recover, what you need to avoid, body scanning, and researching how to FIX your health. Each time I noticed one of these thoughts or behaviors, I redirected it.

This is a common tool employed in many brain rewiring algorithms, I call it the Pattern Interrupt (and I now teach it early on in my Level 1 program, Regulate™). I then brought in positive visualizations to disarm my hippocampus from being stuck rehearsing my past traumas, and elevated my mood to switch off the constant alarm bells sounding from my amygdala.


Quickly, brain retraining became one of the first methods that I took seriously in my recovery from Lyme disease and chronic fatigue. I wasn’t taking medicine or supplements, I didn’t have any money at that time to do anything like that, but brain retraining was powerful. It shifted my symptoms very quickly.

I started to craft a roadmap to navigate me out of the dense fog of my illness and fear. Beyond the brain retraining, I delved deeper into the art of self-regulating my nervous system, including somatic trauma release, vagus nerve toning and functional neurology exercises that I had learnt from my training as a Physical Therapist.

Remarkably, I discovered the ability to experience genuine joy and tranquility despite facing challenging symptoms and limitations. It was a turning point – my nervous system began to transform.

As my brain rewired itself and built new neural pathways, a newfound trust in my body’s healing potential blossomed within me. I unearthed the essence of “primal trust” – the resonance of safety and connection – and chose to let it awaken my body’s innate capacity for healing. To my astonishment, one by one, symptoms began to dissipate as I continued to embrace these tools of self-regulation and trust.

So How Does Brain Retraining Work?

Recent studies have shattered the long-held belief that the adult brain remains static after birth, revealing its remarkable plasticity and ability to change and adapt through a process called neurogenesis. Neurogenesis refers to the process by which new neurons, or nerve cells, are generated in the brain.

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Norman Doidge’s book, “The Brain That Changes Itself,” presents compelling stories of individuals who defied traditional scientific understanding by transforming their brains through various practices.

Neurogenesis, the generation of fresh neurons, offers promising implications for healing brain injuries and other chronic illnesses, reversing aging effects, resolving anxiety, and enhancing memory and intelligence.

The adult brain possesses a finite number of neurons, which were previously thought to diminish over time. However, groundbreaking research has shown that the brain can regenerate neurons, challenging the notion of irreversible decline with age. Brain retraining is an example of a powerful tool we can use to maximize neurogenesis. Studies have demonstrated that meditation stimulates neurogenesis in the hippocampus, a brain region crucial for learning and memory, and brain retraining works similarly.

How Does the Vagus Nerve Tie In?

The vagus nerve is the longest nerve in the body, stretching from the brainstem, extending down through the neck, chest, and abdomen, and ultimately ending in the colon. It helps control many important bodily functions, influencing heart rate, breathing, digestion, and – as the above linked article shows – the immune system. It is also involved in the body’s stress response system, where its job is to activate the parasympathetic nervous system (“rest and digest” response) and put a brake on the sympathetic nervous system (“fight or flight” response).

The vagus nerve transmits sensory information between the brain and body and back, such as information about heart rate, breathing and digestion.

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An infographic to show how many things the vagus nerve influences in the body. When we stimulate the vagus nerve, we help switch on the body’s ability to rest, digest, detoxify and heal.

Because the vagus nerve is one of main controls of organ function and can be an on/off switch for health or illness, I believe vagal toning exercises should be included in all healing protocols.

Vagus nerve stimulation exercises help to strengthen the communication channel between the brain and body. The vagus nerve is crucial in the body’s ability to perceive internal bodily sensations and send messages back to the brain to regulate body function (we call this interoceptive awareness). The vagus nerve also sends signals from the brain to the body. So by stimulating the vagus nerve, we are not only turning on the calming parasympathetic nervous system response, but we are strengthening the superhighway that allows for optimal and healthy communication between the brain and body.

I made this connection years ago when I started to see tangible results from brain retraining, but felt there was something missing. When I added in vagus nerve toning and other body-based practices designed to release stress and trauma, my healing exponentially increased. It’s what I now teach others through the Primal Trust™ Academy & Community.

What Can You Hope to Heal?

Eventually, my reward from retraining my brain and vagus nerve toning was vibrant health and a life filled with purpose and joy. But trust me when I say, if I can do it, you can do it too. I am not a guru, and I don’t claim to have reached some pinnacle of perfection from doing this work. I still have my struggles in life like we all do. But what I have discovered is our body and brain have a huge and often untapped potential for self-healing, and the mind-body connection is very real and not as woo as it sounds.

In our community, we have seen some remarkable results from implementing this work.

Catherine Hyza, who reversed Hashimoto’s and 35+ symptoms in an astonishing 4 months…

Kelly Barber, who was unable to stand without chronic and debilitating pain, now hikes pain-free and is planning a life with her fiancé.

Marla Hall, who was scheduled to have 80% of her colon removed due to colonic inertia, now has a healthy and functioning digestive system.

These are just some examples, and we have many more, of the self-healing that’s possible when you learn how to retrain your brain, switch off the limbic system’s alarm response, and send signals of calm to your body through your vagus nerve, allowing your immune system – and many other systems in the body – to come back online.

Cathleen King, DPT

I'm an expert on chronic illness, chronic trauma, relationship/attachment repair, and inner child healing. I’ve got the rare combination of in-depth doctoral-level education and training as a physical therapist, and many years of coaching others in wellness and lifestyle education. And, I have been through my own heroine’s journey of spending nearly 2 decades of my life navigating through deep, debilitating illness and finally found my way out!

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