Physiology of Emotion


Let’s be sentient

Let’s have eyes and ears and kinaesthesia.

Let’s dream by day and love with purpose.

Let’s notice. Let’s discover.

Let’s feel.


Some history of emotion

Deep inside the great forest of the cerebellum and stretching into major parts of the midbrain we find some very old structures of the central nervous system usually referred to as the limbic system. The limbic system came into existence when we were still prehistoric water creatures, swimming around in the waters of some 400-500 million years ago. There has been much speculation as to why these very advanced structures along with the olfactory bulbs, the optic tectum and the basal ganglia suddenly developed with record speed.

According to the most prevalent theories, a prehistoric sea creature dubbed the urbilaterian (referring to the hypothetical ‘original’ bilaterian creature) spontaneously duplicated its entire genome. This left a lot of potential genes for evolution to toy around with and thus, quite unanticipatedly, lots of intelligent structures evolved almost simultaneously.

The limbic system has four major parts: The thalamus, the hypothalamus, the hippocampus and the two amygdalae. These four chambers orchestrate (amongst many other things) the recording of experience, tracking of danger and a complex signalling system to avoid or encourage behaviour based on said recorded experience.

The complex signalling system is what we think of as emotion. It regulates a creature’s behaviour by distributing unpleasant or pleasant signals through the nervous system. The signals themselves are recorded and reinforced when repeated and ultimately generate intensified programs to further encourage or discourage behaviour. These signals trigger physical responses through the autonomic nervous system, regulating the activity of organs, glands and various movements.

Let’s, just for a moment, try to see in front of us this little sea creature rapidly evolving new and fragile structures to aid its survival. What do you think it feels? The first feeling in known creation – what could it have been? Was it fear? Or was it ecstasy?

How much of reality does it really experience? Is it at all sentient? Is it aware of its revolutionary mutations?

Prefrontal Cortices

We have evolved much since then. Already 200 million years ago the very first mammals evolved tissue on top of the mesencephalon, displaying the first layers of what would become the neocortex. Regular mammals also have a neocortex, it is not exclusive to humans, but humans have evolved a much larger structure than all others.

Phineas Gage was a 19th century American railroad foreman who suffered an extraordinary accident. When 19th century railroad workers were clearing out rock they would drill a hole, fill it with gunpowder and pack it, using a long tamping iron. In 1848 Gage was overseeing the building of a railroad from Burlington to Rutland, and whilst packing the friction from the tamping iron caused the gunpowder to explode, propelling the large instrument straight into his left cheek and through his right eye socket. His face was smashed, he lost an eye and the frontal lobe was completely ruined. But, as a surrealistic as it may seem, Phineas Gage survived and lived on for another 12 years after the accident.

At that time the prefrontal cortex was thought to have no notable function. In fact, the name cortex means “bark”, suggesting that the cortex is a mere protective cover for the more important structures underneath. But 20 years after the accident, several years after Gage’s own death, his doctor published and spoke of the great changes that had occurred in his personality post trauma.


“The balance between his intellectual faculties and animal propensities, seems to have been destroyed. He is fitful, irreverent, indulging at times in the grossest profanity (…), manifesting but little deference for his fellows, impatient of restraint of advice when it conflicts with his desires, at times pertinaciously obstinate, yet capricious and vacillating, devising many plans of future operation, which are no sooner arranged than they are abandoned in turn for others appearing more feasible.”

-Dr. John Martyn Harlow

Dr. Harlow, and indeed Phineas Gage, had discovered what became the foundation of understanding this incredible and powerful region. It does not initiate but carefully regulate thought, emotion and movement based on very intelligent observations in its context. It is thanks to this region that we can experience the intersubjective, organise ever larger societies, plan the future and develop information channels through history like culture and tradition. As well as to lie, deceive, act and pretend. As Phineas Gage has shown us, without it we are animals.

When Dr. Farias explains this he carefully mentions that people with low activity in the prefrontal lobes find social life to be difficult because they think, feel and act in ways that are deemed inappropriate. This is often the case for patients of dystonia and, I would assume, a quite normal situation for other highly sensitive people.

The Autonomous Nervous System (ANS)

The Autonomous Nervous System (ANS) is the category of neural circuits working beyond our conscious influence. These circuits oversee and regulate the organs, the heart, the hormonal glands and the smooth muscle cells.

The autonomous nervous system has two general divisions: Sympathetic (SNS) and Parasympathetic (PNS). The first is related to fear response and is usually dubbed “Fight or Flight” while the second is dubbed “Rest and Digest”. These two divisions are independent systems with separate circuits that operate in tandem as instructed by the limbic system. Regular and effortless shifting between the two systems is the goal, primarily responding to the internal environment of the body to help maintaining homeostasis.

Homeostasis is the balance of all things in the body, such as temperature, acidity, water content, sugar levels in the blood, et cetera. When it is disrupted the central nervous system reacts in attempt to restore balance. If homeostasis is not restored it will have many troublesome effects and may cause all sorts of deficiencies like diabetes, heart failure and death.  

If a person finds himself in chronic stress the homeostasis is disrupted, and the nervous system will have increased innervation of SNS and a decreased activation of the PNS. Because most neurons are adaptive the feeling of stress will dissipate over time. Stress will become the new “normal”.

This is crucial because most people who live with chronic stress do not notice that they are stressed. Neural adaptation exists because the nervous system wants to be especially sensitive to changes in the environment and to quickly adapt to whatever context it finds itself in. When the stress does not dissipate it is regarded as “normal” and the feeling of being stressed will disappear. But the SNS will carry on its functions which involves, amongst many other things, reducing metabolism, releasing epinephrine from the adrenal glands, increasing heart rate and blood pressure and decreasing salivary production.


“Is it really possible to tell someone else what one feels?”

                -from ‘Anna Karenina’ by Leo Tolstoy

Your emotions and you

The point of this post is to give emotions a physical appearance. The people in my life usually talk about emotions as if they’re made up or somehow abstract. This is untrue. Emotions are as physical as hands and hearts and ignoring or suppressing them has an equally abusive effect on the body as any physical damage would.

Our experience of life is ultimately dependent on the way these structures are interacting and affecting each other. We can see lots of indirect effects: Low metabolism can be resulting from depression because the sympathetic nervous system downregulates this as instructed by the limbic system during chronic stress. If you smash your amygdalae you will experience no fear. Which sounds tempting but is really dangerous.

Every emotion gives a sensation somewhere in the body. Often these signals make little sense, like tingling in the stomach, a lump in the throat or a black heart. These sensations are part of the emotion. This is what you ‘feel’. When you notice, accept and focus on these sensations the feelings will process and dissipate. If you fight, they will persist. If you avoid, they will remain. Only by welcoming your feelings can you befriend them and liberate yourself.

I hope that with this information we can all be more concerned with our own emotional health because, as I am experiencing, in time it will have a very real, very physical impact.