How is disgust processed in the brain?

Disgust is one of the basic emotions and has helped us survive throughout our evolution. And, although it has been one of those forgotten by psychology, we already have enough information about how the brain processes disgust: a feeling of strong dislike towards some substances or objects, which produces the need to expel it, distance it or reject it.

This emotion is universally considered one of the six basic emotions, identified in all cultures and people with sensory limitations. Has a characteristic facial expression: raising of the upper lip, frowning and lowering of the corners of the mouth.

In addition, it is accompanied by a drop in tension, a decrease in the galvanic response of the skin, nausea, a decrease in heart rate, a feeling of aversion, distancing from the object, respiratory changes, and characteristic vocalizations (for example, “ughh!“). Let’s see it in detail.

nature of disgust

It is important to keep in mind that the brain has been shaped by our experience – both as a species and as an individual. So, Before we had a developed immune system, we had a kind of behavioral immune system.

The advantage that feeling disgust has given us has mainly been the avoidance of diseases. Thus, although there are cultural differences about what makes us sick, the main triggers of this emotion are:

Secretions and body parts: feces, saliva, blood, wounds, vomit, feet, etc. Rotten food. Some living beings such as insects, worms or spiders. Some characteristics of unknown or different people. Violations of social or moral norms.

Even though it is an innate emotion, It must be taken into account that some aspects of disgust are learned, giving rise to cultural or developmental differences.. For example, children up to two years old do not seem to feel disgust.

However, this could be explained because, up to this age, they are under the care of their parents and because our species is born quite immature and vulnerable. Thus, by observing the parents’ behaviors, the emotion would develop.

Disgust in the brain

To know how disgust is processed in the brain, two fundamental regions must be taken into account: the insula and the limbic system (amygdala and hippocampus). Let’s see them separately:

The insula It receives information from sensory pathways and sends information or stimuli to other structures, such as the limbic system, ventral striatum, and orbitofrontal cortex. This region seems to be responsible for experiencing disgust, as well as recognizing expressions of disgust in other people. For example, in people with Huntington’s disease, where the insula is affected, alterations in this emotion are found. Additionally, stimulation of the insula produces nausea. limbic system, and specifically the amygdala, is related to negative emotional processing, like fear and disgust, and with learning. In fact, recently, a group formed by members of the University of Granada and the Autonomous University of Baja California have detected the specific region of the amygdala that causes rejection of unpleasant flavors.

How do you process it?

Until now, scientific studies have linked disgust to certain brain areas, capturing images of the areas involved. Now, Thanks to technologies, such as functional magnetic resonance imaging, it is possible to observe how disgust is processed in the brain dynamically.

This is what a group of researchers from Catalonia did a year ago. To do this, 30 people were subjected to a study in which, within the MRI, they were presented with six minutes of video of appetizing foods, compared to six minutes of food and other unpleasant objects (cockroaches or men eating worms, among others).

The results have shown that even 40 seconds after observing the unpleasant images, the brain continues to process this emotion. Furthermore, brain imaging has shown that when faced with a disgusting scene or object, Not only is one part of the brain activated, among those indicated above, but almost half of the brain is activated..

Regarding processing, scientists have stated that there are three phases. You have them below:

The stimulus appears and the brain begins to activate defense and protection mechanismseven without the person being conscious. A second phase of conscious alert in which the you begin to consciously value the stimulus as negative.A third phase of assimilation, in which the emotion of disgust is felt and causes the experience to be stored in memory. This phase can last about 26 seconds afterwards.

Disgust disorders

It may happen that you feel excessive disgust or towards stimuli that initially should not provoke it. So, There are several psychopathological disorders that are related or have a specific disgust component.

In some phobias, the disgust component is crucial, as in blood phobia or social phobia. Regarding the latter, it seems that in some cases the person feels a certain repulsion or aversion to interacting with people. Also, the role that disgust has in eating disorders is being investigated.

In short, disgust is a primitive, adaptive emotion with a well-defined and established neural correlate. As unpleasant as it may be at times, remember that you are probably here because your ancestors decided not to eat that brightly colored spider or live near its latrines.

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