Brain-body connection: why is it important for resilience and cognition?

Ever wondered why you might feel anxious when you are sick? Or if mindfulness can really help improve your resilience, or why kangaroos don’t build rocket ships? The answer lies in the relationship between brain and body. A growing body of fascinating scientific literature is shedding light on the relationship between the mind and body in a Defence context. Military strategists have emphasised that the strength needed to win the next war will be less about kinetic energy than about cognitive power and performance (Scales, 2009).

The Prefrontal Cortex and Autonomic Regulation: Crucial Brain Structures for ADF Personnel

Our brains contain evolutionary distinct structures. Part of the outer layer is the Prefrontal Cortex (PFC), a relatively new structure in evolutionary terms. A well-functioning PFC is crucial for performing many higher-order cognitive functions, such as decision-making, planning, problem-solving, attention, working memory, and social behaviour. Therefore, the PFC is a crucial brain structure for the Australian Defence Force's (ADF’s) current and future roles.

Below the outer layer lies a vast landscape of subcortical brain areas. Most of these areas are involved in regulating bodily functions and ensuring our basic bodily needs are met, such as urinating and breathing. Most of the time, we are not aware of this, which is helpful so we can focus on our environment. The feeling that you are busting to go to the toilet is not particularly helpful if you have to make life-or-death decisions. A study found that when aircrew members voluntarily hold in their urine, their cognitive performance decreases. This finding comes from a recent study involving defence personnel. (Griswold et al., 2023).

The Role of the Amygdala and Interoception in Emotional Processing and Cognitive Function

One particularly interesting subcortical brain area is the amygdala. This is a small structure about 1.5 to 2 cm in length and weighing approximately 1.5 grams. Despite its small size, the amygdala plays a major role in our brain. It automatically tags the significance and intensity of incoming information, such as pain, vision, and sound. The amygdala can orchestrate automatic survival responses, such as screaming, startling, or freezing when frightened.

For example, if you encounter a kangaroo at dusk on the road, they will usually freeze in response to the headlights. This is a typical amygdala response. How the amygdala tags incoming information as dangerous or not, is mainly dependent on learning and life experience. For example, if you have ever been bitten by a dog, there is a big chance that your amygdala will remember this and next time you see a dog, your body will be ready to fight-or-flight.

The PFC, amygdala, and other brain structures form a network called the Central Autonomic Network (CAN), which is involved in regulating autonomic functions such as heart rate, blood pressure, and respiration (Goldstein, 2019). Scientists are actively investigating the mechanisms of this network and how various factors – such as stressors, cognition, emotion, and body functions – interact within it.

Stressors can refer to any external or internal stimuli that trigger a stress response in the brain. These stressors can be perceived through our senses, such as sight and sound, or they can arise from our bodies, such as inflammation. The CAN plays a crucial role in coordinating the body's response to these stressors, helping to maintain internal stability and homeostasis.

Emerging research suggests that the CAN may also be involved in regulating immune function, highlighting the complex interplay between the brain and the immune system. For example, a Mediterranean diet, healthy gut, and regular exercise have all been associated with better health, emotion, and cognition, in part because they are linked to lower inflammation markers in the body (Beavers et al., 2010; Schwingshackl & Hoffmann, 2014; Singh et al., 2017). These findings underscore the importance of understanding the intricate connections between the brain and the body and how they contribute to overall health and well-being.

Members of the ADF often face unavoidable stressful situations during missions and training, such as sleep disturbances, limited food and water availability, and physical exertion. These stressors can trigger a range of physiological responses that are processed and integrated in the brain. Your awareness of the internal state of the body is known as interoception. This includes sensations from internal organs that you are aware of, as well as those that you are not aware of, such as the heart, lungs, stomach, and intestines. Phrases such as "it's just a gut feeling" suddenly become very meaningful.

Building Resilient Brains: Mindfulness, Biosensors, and Healthy Development.

Maintaining goal-directed behaviour is critical for mission success, even in the face of significant physical and psychological stressors. The processing of interoceptive signals occurs in a brain region that is also involved in cognitive top-down demands, suggesting that this area plays a key role in balancing external environmental demands with internal physiological needs. A better ability to process this interoceptive information is linked to better emotional processing, self-regulation, and better cognitive functions – such as sustained attention, working memory and cognitive control (Tsakiris & Critchley, 2016).

There is evidence that highly resilient individuals, such as elite athletes or special operations forces, show better processing of interoceptive information. For example, they show better performance on tasks that require emotional processing and on physical tasks such as breathing against a resistance (Haase, Thom, et al., 2016; Simmons et al., 2012). On the flip side, low resilience is linked with low interoception (Haase, Stewart, et al., 2016).

Interoception, Emotion, and Physiological Links

Interoceptive signals have been suggested as generators for our emotions. Both perceived and unperceived interoceptive information contribute to emotions. For example, infectious illness often coincides with feelings of anxiety. There is a shared pathway between inflammatory signalling and stress-related signalling. In addition, there is growing evidence on the role of bodily stressors, such as inflammation, on human cognition. This would mean that our physical state, emotions, and cognition are physiologically linked.

So how is your interoception related to emotional processing? The brain does not just perceive information, it also uses prior information to make predictions about future states. When there is a difference between the expected state and incoming information from the body, a "prediction error" occurs. These errors can trigger emotional responses, such as anxiety, surprise or fear, and homeostatic adjustments, which may motivate us to take action to reduce the error.

For example, imagine you are walking down a dark alley and hear a sudden noise. Your brain immediately predicts that the noise is a potential threat and prepares you to respond accordingly (e.g. by running away or fighting). However, if the noise turns out to be nothing dangerous (e.g. a cat jumping out of a garbage can), your brain has made a prediction error. This prediction error is then thought to lead to an emotion, in this case the feeling or surprise of relief.

Mindfulness and Brain Activation

Researchers are testing mindfulness as a method to reduce this prediction error. This results in less intense emotions and improved cognitive function, potentially because you have to spend fewer resources on trying to figure out what is happening with your body. Previous studies with Defence personnel have shown that mindfulness can enhance well-being, working memory, and emotion regulation (Jha et al., 2010).

A more recent study investigated whether mindfulness training modulates neural processing of interoceptive distress in infantry Marines scheduled to undergo pre-deployment training and deployment to Afghanistan (Haase, Thom, et al., 2016). The results supported the hypothesis that mindfulness changes brain activation, allowing individuals to process aversive interoceptive stimuli more effectively.

Therefore, mindfulness may serve as a training technique to modulate the brain's response to negative interoceptive stimuli, which could help improve resilience. At the start, we mentioned the PFC, our action hero. The PFC has a direct connection with some of these subcortical brain areas, including the amygdala. This allows humans with the unique capability to exert some control over these automatic subcortical brain areas. Neuroimaging studies have shown that mindfulness can change the brain and improve the connection between the prefrontal cortex and the amygdala. A better connection allows for better regulation of emotions (Marchand, 2014).

The stress response is evolutionarily beneficial, ensuring our bodies are ready to fight-or-flight by increasing our heart rate, blood pressure, and pupil size. However, high stress levels can also literally turn off the PFC, resulting in an inability to perform higher-level cognitive functions. As a result, behaviours are driven by reflexes and conditioned responses. This can be useful for our survival in a physical fight but is detrimental for higher-level cognitive functions, such as decision-making, planning, as well as social and moral behaviour in conflict situations.

Building a Strong Prefrontal Cortex (PFC)

The PFC and subcortical brain areas need to communicate effectively for optimal self-regulation and cognitive performance. The PFC, which plays a crucial role in decision-making, problem-solving, and emotion regulation, continues to develop until around the age of 24. During this developmental period, the PFC is particularly vulnerable to negative influences such as alcohol, smoking, and chronic stress, which can impair its functioning and development.

However, this also means that there is a critical time window during which we can actively build resilient brains. By providing positive experiences, supportive environments, and engaging in healthy habits, we can promote the healthy development and maturation of the PFC and its connections to other brain areas. This can lead to better self-regulation, emotional regulation, and cognitive performance, which are essential for success in various domains, including academic, social, and military settings.

The CAN network also needs some challenges in order to develop properly. Similarly, just recovering when you are training for a marathon won’t help you run a fast marathon time. There is also a notion in sport psychology that ‘trauma makes talent’, based on the observation that many elite-level Olympians have experienced a traumatic experience in their youth (Collins & MacNamara, 2012). Early life stressors or challenges with appropriate support might make individuals more resilient. There is indeed evidence that structural changes occur in the PFC during early mild life stressors, resulting in individuals that are more resilient. Chronic stress on the other hand can cause neurons to shrink in the PFC and grow in the amygdala, which diminish resilience. In young animals, these effects are reversible; however, ageing seems to compromise resilience and PFC recovery.

Studies suggest that a range of interventions can strengthen the connection between the PFC and amygdala. These for example include brain stimulation, mindfulness meditation, cognitive-behavioural therapy, and exercise (Wang et al., 2024). This means that the two most practical cases, physical activity and mindfulness, do not only make your body stronger but potentially also enhance your mind and emotion regulation abilities.

The PFC is responsible for various functions, including impulse control and learned fear extinction. Stronger PFCs in humans have been linked to reduced impulsivity, while elite athletes show better inhibitory control of the PFC compared to non-elites. The amygdala, on the other hand, plays a crucial role in processing emotions, particularly fear and anxiety. A strong PFC can help regulate the amygdala's activity, which is essential for building resilience and emotion regulation.

Therefore, I think that becoming elite is not only about getting as fit as possible to stretch the limits of what your body can tolerate, but also about building a strong PFC to quieten down your screaming amygdala. In summary, a well-functioning PFC that can effectively control subcortical brain areas, including the amygdala, is critical for building resilience, emotion regulation, and cognitive functioning.

Conclusion: Promoting Resilience, Emotional Regulation, and Cognitive Functioning

There are a few deliberate actions to support a healthy development of the CAN. First, ensure that children are not exposed to excessive stressors. These include environmental stressors, but likely also include physiological stressors, such as chronic inflammation. Chronic inflammation has been linked to a range of negative health outcomes, including impaired brain function and increased risk of mental health disorders (Jiang et al., 2018; Kohman & Rhodes, 2013). By promoting healthy eating habits, and encouraging regular exercise, we can help reduce the burden of chronic inflammation and support healthy brain development.

Secondly, incorporating evidence-based programs of mindfulness will likely help strengthen the connection between the PFC and amygdala, promoting self-regulation, emotional regulation, and cognitive function. This might also equip the future generation with strategies to manage their stress levels. This might result in a happier and more resilient society.

In conclusion, supporting the development and maintenance of a healthy CAN, particularly the connection between the PFC and subcortical brain areas, is crucial for promoting resilience, emotional regulation, and cognitive functioning. While this is especially important for future generations, there are also steps we can take now to support our people.

Reducing chronic stressors as much as practical, such as excessive workload, poor diet, and lack of sleep is essential for maintaining a healthy CAN. Additionally, incorporating evidence-based interventions such as mindfulness, cognitive-behavioural therapy, and physical exercise can help strengthen the connectivity between the PFC and subcortical brain areas.

Biosensors such as heart rate monitors can also play a role in tracking physiological stress levels and preventing maladaptive changes in emotional and cognitive functioning. This could serve as early markers for intervention. Furthermore, exploring the effectiveness and practicality of these interventions can help us better understand how to promote resilience and well-being in various contexts.

In summary, while kangaroos may lack a PFC and hence the cognitive capacity for rational decision-making, humans have the unique ability to use their PFC to plan for the future and make adaptive choices. By prioritising the health of the CAN, we can promote resilience, well-being, and cognitive functioning, both now and in the future. So where does this leave us? In my opinion, building a resilient Australian society starts early in life. This will benefit the ADF since the next generation soldiers, leaders, athletes, and scientists are the children currently in our schools. Their future ability to thrive in the face of adversity will have implications for our nation’s future.

If your PFC would like to engage with mine, just send me a message.

References

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Collins, D., & MacNamara, Á. (2012). The rocky road to the top: why talent needs trauma. Sports Medicine, 42, 907-914. 

Goldstein, D. S. (2019). How does homeostasis happen? Integrative physiological, systems biological, and evolutionary perspectives. Am J Physiol Regul Integr Comp Physiol, 316(4), R301-R317. https://doi.org/10.1152/ajpregu.00396.2018

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