Darwin already saw emotions linked to neurology and physiology – 12/04/2023 – Luciano Melo

Charles Darwin, in 1872, argued: emotions are mental states that cause stereotypical bodily reactions. For Darwin, each feeling could be precisely identified in specific facial postures and movements. For this there would be a universally repeated route, which connects this brain product to the muscles.

When active, the emotion is revealed by an exact expression. This idea was one of the inspirations for the technical dawn that transformed psychology, until then mental philosophy, into a scientific discipline. Researchers began to look for physical bases to explain fear, anger and sadness based on neurology and physiology.

The human mind was seen as a set of separate capacities and each of these would be produced by a particular anatomical substrate. At the time, discoveries were emerging that exact brain locations took care of restricted functions such as language and vision. Why wouldn’t there be areas that hold anger, fear and joy?

Scientists Klüver and Bucy in 1939 gave good answers to this question. The duo observed the missing parts that were eliminated in the brains of monkeys. Primates whose limbic systems – a set of structures at the base of the brain – had been damaged, changed from ferocious to docile animals. Before the intervention, they would move away from venomous animals in disgust, and afterwards, they would even bring them to their mouths. The intracranial center for anger and fear had been discovered. Decades after Klüver and Bucy, new research showed that a part of the limbic system, the amygdala, should be considered this emotional core. Under this view, feelings battle with cognition to control behavior.

Sophisticated brain imaging techniques in humans prove that the amygdalae function in fear and panic and emotional conditioning. They also format memories with emotional attachments and enable us to recognize the facial expression of fear. But these conclusions were drawn from laboratory experiments. Real-life examples of people with brain injuries restricted to the amygdala are essential for more refined knowledge.

There is a rare genetic defect that causes Urbach-Wieth disease, the consequences of which spread throughout the body and in particular lead to calcification of the cerebral tonsils. SM is a woman who has this diagnosis, she had difficulties experiencing fear in normative moments; for example, when watching horror films. SM fails to learn from its mistakes and barely recognizes the fear expressed on faces and tones of voices. However, in special circumstances, when she inhales air with higher concentrations of CO_two, she panics. The amygdala, therefore, is not fundamental to the sensation of fear. Another point: not all people with bilateral tonsil lesions suffer from the same restrictions experienced by SM

Contrary to what Darwin thought, there is no single expression definitely linked to an emotion. And if we want to understand these feelings, it is insufficient to look at one area in our body, the entire brain matters. This body contains specialization modules, but has another characteristic opposite to this attribution. Several of its elements, structured in different locations, have a similar function and promote the same behavior. Natural selection favors systems like this, which demonstrate complexity and resistance to damage.

The activity of a single neuron, or a small grouping of them, is the presence or absence of some brain function, at a given moment. Many neurons connect with a single one, called many-to-one connectivity. Therefore, the activity of one of these cells receives influences from different combinations exerted by its peers. As a consequence, neurons have multiple purposes.

And so the different brain regions, although specialized, carry out different responsibilities. And many of these transform neural events into mental categories, which we assign meaning and name. Sadness, anger, disgust are examples of these categories. These are guesses about our internal situation. This is a crucial process for us to learn from experience, and for us to infer what is about to happen.

The brain did not arise for reason, happiness, or accurate perception. If this were the case, energy consumption would be immense and unsustainable. Restricted by deprivation, the brain creates mental models to understand the instant, based on assumptions. Forming emotions is a brain way for us to have mental maps of our insights, and to give meaning to the influence that the environment has on our bodies. It is our brain’s way of explaining the bodily sensations that arise as a result of the situation around us, and internally. Emotions are not just reactions to the environment, but a way of understanding consequences. They are diffuse works of our brains and unstable, no sensation is exactly the same as what just happened.

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