Introduction
Understanding the nature of emotions as the factors that serve not only to represent a response to a specific stimulus but also as the means of gauging an individual’s psychological well-being is central to modern psychology. Remarkably, despite being an intuitively understandable concept, the phenomenon of emotion does not have a clear definition based on the current knowledge of the brain and its functions (Kringelbach & Berridge, 2017). Neurologically, emotion is usually defined as the “the cause of actions and physical changes in the body, giving rise to the folk intuition that emotions are central drivers of behavior and experience” (Hoemann & Barrett, 2019, p. 69).
However, as Kringelbach and Berridge (2017) explain, in seeking the exact definition of the subject matter, no consensus has been reached so far. Despite there is presently no agreement on the issue of defining emotion, it could be argued that emotion is a product of the performance of the amygdala, hypothalamus, and insular cortex, which provide a chain leading to the emergence of an emotional response toward a specific stimulus.
This essay will discuss the mechanism of developing emotion in humans. Namely, the essential functions of the key parts of the brain that cause an individual to experience emotions will be described and discussed. It is believed that this paper will contribute to building a more accurate and nuanced understanding of how emotions are formed by providing an amalgamation of the available research on the topic. Moreover, the key conclusions made in these studies will be assessed and incorporated into the general statement concerning the neurological nature of emotions. The paper will consist of the description of the role that the amygdala plays in the development of emotions, followed by a corresponding part addressing the role of the insular cortex, then the discussion of the hypothalamus, and, eventually, end in a conclusion.
Amygdala
The amygdala is often mentioned in discussing the mechanism of emotions. By definition, the amygdala is “a brain structure that regulates behavioral, autonomic, and endocrine responses” (Reybrouck et al., 2018, p. 9). In other words, the amygdala represents a part of the brain that processes intense emotions, of which fear represents the strongest one. Ferry (2017) mentions that, when examining the nature of fear and the related emotions, one must distinguish it from anxiety since the two phenomena are produced with the help of different brain circuitries. However, it is important to stress that the amygdala’s primary function is to respond to key stressors in the way that involves the development of both fear and anxiety (Ferry, 2017). Therefore, the two functions of the amygdala in relation to the management of stress-inducing factors are worth considering.
When determining the role of the amygdala in the development of emotion in humans, fear must be mentioned as the key emotion for the development of which the amygdala is responsible in humans. Specifically, the study by Orem et al. (2019) shows that the sense of fear is developed as the sensory organs deliver information about an imminent threat to the brain, allowing it to perceive the danger as such, thus, activating the amygdala. In turn, the paper by Seo et al. (2021) shows that the amygdala sends signals to adrenal glands in order to release stress hormones, particularly, neurotransmitters such as cortisol, adrenaline, and the corticotropin-releasing hormone (CRH). The study by Bhagat et al. (2020) concludes that the specified process activates the so-called, resulting in an individual experiencing fear as the emotion signaling that there is an immediate threat to life or well-being.
Furthermore, studies that prove the connection between the functioning of The amygdala and the emergence of fear are quite substantial. For instance, the paper by McFadyen (2019) establishes that there is an unambiguous link between the functions of the amygdala and the experience of fear:
We discovered that fibre density along only the second half of the subcortical route significantly covaried with effective connectivity (i.e. people with greater fibre density also had stronger pulvinar-amygdala functional coupling) as well as better recognition of fearful (but not angry or sad) expressions. (McFadyen, 2019, p. 2)
Therefore, the role of amygdala in the development of fear as a response to the factors that people typically recognize as the source of danger or a threat can be confirmed. At the same time, the authors confirm that the specified area is severely underreacted (Orem et al.), 2019. Particularly, further studies are required to understand the relation of each circuit individually to the development of a fear response. Thus, a better understanding of the emotion development mechanism will occur.
Insular Cortex
The insular cortex is a lesser known yet nonetheless important part of the brain in developing emotion. In neuroscience, the insular cortex is defined as “a distinct, oval-shaped group of gyri, located deep within the Sylvian fissure” (Coolidge, 2019, p. 80). Researchers also point to the uniquely complex structure of the insular cortex, underlying its role as the hub in the process of emotional guidance, among other multiple roles that it plays in the human body (Coolidge, 2019). In essence, the functions of the insular cortex can be summarized as those of a mediator between the brain regions that supply sensory information, perform cognitive functions, develop emotional responses, and contribute to the emergence of motivation. Therefore, the insular cortex plays a tremendous role in the development of emotions in the human brain.
When singling out the emotional responses associated with the function of the insular cortex, studies typically mention disgust as the essential one. Specifically, the study by Viol et al. (2019) explains that the role of the insular cortex in the development of disgust by connecting it to the function of a hub mentioned above. Namely, since the insular cortex performs the functions of a mediator that connects the rest of the brain areas in the process of analyzing information, it can be seen as a “salience network” within the brain (Schienle & Wabnegger, 2021, p. 6). In turn, once a sensory input that disrupts the described state of salience emerges, the insular cortex reacts immediately, producing a response that forces an individual to see the source of it as disgusting (Viol et al., 2019).
However, there are also indications that the insular cortex is not the only contributing factor in the development of disgust as an emotional response to unpleasant experiences. Namely, the paper by Kavaliers et al. (2018, p. 9) establishes that the exposure to unpleasant odors in participants of their research has led to an increased activity in the “orbitofrontal cortex, piriform cortex, amygdala and insular cortex.” Therefore, it would be a mistake to attribute the entire experience of disgust as an emotion to the insular cortex. Instead, further studies should be conducted to establish the exact function that each of the brain parts in question plays in the experience of disgust as response to a negative stimulus.
Hypothalamus
In contrast to the previously discussed brain parts, the hypothalamus is responsible not of the emergence of a particular emotion as a response to a stimulus, but, instead, for a combination of processes known as the emotional learning. Specifically, the hypothalamus is usually defined as “a link structure between the nervous and the endocrine system” (Baloyannis & Gordeladze, 2018, p. 4). Representing an organ that connects two different systems, the hypothalamus has a range of functions that are not necessarily linked to emotions but, instead, are closely connected to the regulation of the key processes within the human body (Baloyannis & Gordeladze, 2018).
For example, the hypothalamus is a part of the control system for the body temperature, as well as memory processes (Baloyannis & Gordeladze, 2018). At the same time, the hypothalamus also represents a crucial part of the mechanism responsible for the development of emotions (Baloyannis & Gordeladze, 2018). Therefore, allowing the brain to memorize essential emotional responses to a variety of factors, the hypothalamus contributes to emotional learning, namely, allowing an individual to experience the nuances of different emotions.
In order to understand the function and roles of hypothalamus in emotional regulation and the development of emotion, multiple studios have been carried out. Among the most notable ones, it is crucial to mention Falkner and Lin’s (2014) research on mice, which has shown that, similarly to the insular cortex, hypothalamus plays an essential role in the creation of the fight or flight response in humans (Falkner & Lin, 2014). However, it is noteworthy that, instead of fear as the primary response to the factor that represented an imminent threat, the test subjects, namely, mice, showed the propensity toward building aggression and reacting violently to the provided stimuli (Faulkner & Lin, 2014).
The described outcome might seem as surprising, yet it is worth mentioning that aggression is typically linked to fear, specifically, in the very concept of the fight-or-flight response. Therefore, the studies have confirmed that, among other roles that hypothalamus plays in emotion development, its functions include contributing to the experience of fear and aggression (Faulkner & Lin, 2014).
However, there has been no determining statement regarding the role of the hypothalamus in the development of emotions and, specifically, its role in the production of fear and aggression. For instance, several studies that have conducted similar experiments, such as the paper by Oyola and Handa (2017) and Olvera-Maneu, et al. (2021), have not obtained the same results. Therefore, there are yet studies to be carried out in order to discover the exact connection between hypothalamus and the emergence of various emotions, primarily, those of fear and aggression.
Conclusion
Although the nature of emotions has not been fully studied yet from the neurological perspective, the role of the amygdala, insular cortex, and hypothalamus in the development of emotion and the further progression to the emergence of an emotional response can be considered confirmed, as the studies analyzed above have established. Specifically, the overview of the existing studies shows that the amygdala contributes to the emergence of fear due to the release of hormones such as adrenalin and noradrenalin that is caused by the amygdala once a threat is recognized.
Similarly, the role of the insular cortex in the emergence of disgust as a direct response to what the sensory system recognizes as an unpleasant experience, either due to its taste, look, or smell, has been defined. Specifically, the insular cortex as the organ that serves as the medium between the rest of the brain sections helps to process the sensory input that is recognized as disturbing, thus, allowing an individual to perceive the experience as that one of the feelings of disgust.
Finally, the significance of the hypothalamus in the development of motions as a response to external stimuli has been defined. Specifically, hypothalamus appears to serve as the connector between the nervous and the endocrine systems, which is why its role in emotion development has been defined as spurring the emergence of fear and especially aggression as a reaction toward negative experiences. For this reason, the three systems in question, namely, the amygdala, the insular cortex, and the hypothalamus need to be considered together when exploring the development of emotional responses in humans.
At the same time, it is worth keeping in mind that the study of emotions as a product of the nervous system and the result of complex neurological processes occurring in the human brain is not yet complete. Therefore, further research will be needed to examine the role of each part of the brain on the development of emotion. Thus, additional strategies can potentially be introduced to the management of emotional issues, including mental health concerns. Once the mechanism of emotion development is discovered, the chances to manage mental health concerns, namely, mood disorders, will increase.
References
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