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Key points
- Scientists generally consider emotions to be automatic, unconscious physiological reactions to stimuli.
- Emotions play a central and crucial role, integrating physiology, cognition, behavior, and feelings.
- Emotions are more complex than reflexes but simpler than deliberative behavior.
- Understanding how emotions give rise to subjective awareness (feelings) is key to understanding consciousness.
Amy,1 a 17-year-old patient of mine, is an intelligent young woman who is about to start an engineering program at a top Canadian university. But, frustratingly and distressingly for her, she has always had difficulties with emotional regulation, manifesting as a propensity toward high levels of anxiety, oversensitivity, and low frustration tolerance. In her interactions with family, she is prone to “meltdowns” and not infrequently explodes in temper outbursts. Outside of the home, she usually bottles things up, holding her emotions in until she gets home, often on the verge of tears. Her angry verbal outbursts toward her parents can be particularly nasty. These tirades are frequently followed by remorseful apologies, tearfully insisting that she did not mean what she said. Despite these difficulties, Amy has managed to do well academically and maintain a few close friendships. But controlling her emotions requires an exhausting amount of effort, and they always threaten to derail her.
Amy’s emotional difficulties are more severe than the average person's. But all of us can relate to the experience of having our emotions erupt from somewhere deep within us and upend our attempts at remaining composed, rational, and self-controlled.
What actually are they?
So, what are emotions? Most of us think we know, since we are routinely and intimately acquainted with them.
Surprisingly, to this day, there is no scientific consensus on what emotions are, and where in the brain they are produced. Among the areas of continuing disagreement are whether or to what degree emotions are the product of deep, ancient subcortical brain circuits or more dependent on evolutionarily newer cortical regions, how widespread emotions are in the animal kingdom, and the relation between emotions and consciousness. This four-part blog series will attempt to delineate and explain the different contemporary positions.
Emotions versus feelings
In everyday conversation, the term "emotion" is commonly used synonymously with "conscious experience of emotion" or "feeling." However, scientists generally consider emotions to be automatic, unconscious physiological and behavioral reactions to stimuli.2 Feelings, in contrast to emotions, are the conscious awareness and subjective interpretation of these bodily reactions, shaped also by personal experience and culture. Scientists differ in the relative emphasis they place on conscious feelings versus automatic emotions, and on the degree to which feelings might be uniquely "constructed” in the brains of different individuals.
Delineating and researching emotions
There are both dimensional and categorical approaches to understanding emotions.
Emotions can be represented along two dimensions: valence (pleasantness to unpleasantness) and intensity (low to high arousal), known as "core affect" in psychological theories.3
Categorical approaches view emotions as occurring in several distinct primary forms, e.g., joy, fear, anger. They can also be categorized into complex secondary emotions that regulate social or moral behaviors, such as shame, guilt, embarrassment, pride, and jealousy. There is ongoing debate about whether these commonly used categories will be borne out by ongoing neuroscientific research, and about their universality.
Most psychological studies of emotion in humans have focused on the everyday sense of “emotion” as synonymous with "feeling" (i.e., conscious experience of emotion). But animal research is focused on behavioral or physiological responses, as animals cannot report feelings. An empirical approach to research thus treats emotions as central brain states that can be studied in both humans and animals, whereas feelings can only be self-reported by humans. Some researchers (e.g., Joseph LeDoux, discussed in part 4) caution strongly against assuming that similarities in behavioral or physiological responses between animals and humans imply that animals experience similar feelings to us. Feelings cannot be reliably inferred from behavior.
Emotions play a central role
Emotions are crucially important for human behavior. They integrate feelings, physiology, and sensorimotor behavior.4 They provoke a wide range of physiological responses throughout the body, including changes in heart rate, hormone levels, and immune function. They affect arousal and cognition, including attention, memory processing, and decision-making. They profoundly affect motivation. Emotions also play a significant role in learning, by reinforcing associations through positive and negative reinforcement. Additionally, emotions contribute to social interactions and communication, impacting how we connect with others and navigate social environments. Thus, they can influence our immediate actions and affect our behavior over longer periods.
More complex than reflexes but simpler than deliberative behavior
The authoritative textbook Principles of Neural Science, in its chapter on emotion, provides the following definition:
“Emotions are neurobiological states that cause coordinated behavioral and cognitive responses triggered by the brain. This can occur when an individual detects a significant stimulus (positively or negatively charged) or has a specific thought or memory that leads to an endogenously generated emotional state.”5
Emotions play an intermediate role in regulating the body's physiology and behavior, situated between the simpler processes of reflexes and homeostatic regulation6 and the more complex processes of cognition and deliberate action. Emotions are more flexible and context-dependent than reflexes but less so than deliberate behaviors.7 They can be viewed as having evolved to produce appropriate responses to environmental and internal challenges that are too variable for reflexes but do not require the full flexibility of cognition.
Humans can regulate emotions through mechanisms like facial expressions, allowing some control over both the feeling and expression of emotions. Non-human animals, however, typically display “honest” signals of their emotional states due to a lack of such control.8
Where in the brain do they come from?
Fear is probably the emotion whose neurobiology is best understood. It is closely tied to the amygdala, in both animals and humans. In Part 4, we will explore the complicated and indirect relationship between the amygdala and the conscious feeling of fear.9
Emotional processing relies on a wide network of brain regions, including the brainstem, hypothalamus, thalamus, amygdala, hippocampus, basal ganglia, anterior cingulate, insula, parietal cortex, and various subregions of the prefrontal cortex. Footnote 10 summarizes the roles played by each of these regions. It should be noted that there does not appear to be any single brain structure that participates in only one emotion. The important and interesting role of the prefrontal cortex in conscious feelings will be further discussed in Part 4.
Why it matters
Emotions influence nearly every aspect of our lives, from personal relationships and mental health to work performance and overall well-being. Understanding how they work is central to decoding the fundamental processes that drive human behavior, decision-making, and social interactions, and for comprehending and treating psychiatric disorders in patients like Amy and countless others who struggle in various ways to control their emotions.
Furthermore, understanding emotions is key to the mystery of consciousness.
In Parts 2, 3 and 4, we will explore the leading theories of emotions, and their relation to conscious feelings.
References
1. Not her real name. This case vignette is a composite of several actual patients.
2. Some scientists consider emotions to be universal – experienced by all people in the same way, though as we shall see in part 3, this assumption has increasingly been questioned by contemporary researchers.
3. The term "affect" is often used synonymously with "emotion," but "emotion" generally refers to a specific and intense affective state usually directed at a particular object or event. "Affect" or "affective state" is a broad term that encompasses all types of emotional experiences, including short-term emotions, longer-term moods, and other feelings. "Mood" generally refers to a relatively long-lasting, more generalized affective state that is less intense than an emotion and not necessarily directed at a specific stimulus or event. A person is always in some kind of affective state, which includes any emotional or feeling state, even if it is neutral (though they may not necessarily be in a distinct mood).
[Click 'More' to view footnotes 4-10].
4. Emotion. (2023). In G. J. Augustine, J. M. Groh, S. A. Huettel, A.-S. LaMantia, L. E. White, & D. Purves (Eds.), Neuroscience (7th ed., Chapter 32). Oxford University Press.
5. Salzman, C. D., & Adolphs, R. (2021). Emotion. In E. R. Kandel, J. D. Koester, S. H. Mack, & S. A. Siegelbaum (Eds.), Principles of Neural Science (6th ed., p. 1046). McGraw Hill.
6. Homeostasis is the process by which the body keeps its internal environment stable and balanced. This includes maintaining consistent levels of things like temperature, hydration, and pH, through complex feedback mechanisms. A simplified analogy is the way a thermostat keeps the temperature constant in a house. Emotions are integrated with the brain’s homeostatic mechanisms.
7. [Salzman & Adolphs, 2021]. Ralph Adolphs, a prominent researcher in the neuroscience of emotion, who is one of the two authors of the textbook chapter cited here and above, favors this particular definition of emotion. Adolphs’s views will be discussed further in Part 3 of this blog series.
8. Salzman & Adolphs, 2021.
9. The amygdala does not produce the conscious feeling of fear. Rather, it is involved in the automatic defensive reactions to threats, such as the fight-or-flight response. It’s worth noting as well that the amygdala is also involved in other emotional responses, including positive ones. Furthermore, certain types of fear, like suffocation panic, involve brain regions other than the amygdala.
10. BRAIN REGIONS INVOLVED IN EMOTIONAL PROCESSING:
-- Brainstem: Primarily responsible for autonomic functions.
-- Hypothalamus: Regulates endocrine functions and homeostasis, and interacts with the autonomic nervous system.
-- Thalamus: Acts as a relay station, processing and transmitting sensory information to the cortex.
-- Amygdala: Central to emotional learning and fear responses.
-- Hippocampus: Essential for forming emotional memories.
-- Basal Ganglia (including the nucleus accumbens): Involved in regulating movements and various aspects of emotional behavior by processing rewards, motivating actions, influencing emotional expression through motor responses, and helping inhibit inappropriate behaviors.
-- Anterior Cingulate Cortex (ACC): Plays a role in emotion regulation, decision-making, and error detection.
-- Insula: Important for emotional awareness, pain perception, interoception (sensations from within the body like hunger and heartbeat), empathy, and feelings of disgust.
-- Parietal Cortex: Involved in integrating sensory information and contributing to the perception of emotions.
-- Prefrontal Cortex (PFC): Plays a crucial role in the higher-order regulation and interpretation of emotions. Social emotions (e.g., empathy and guilt), reward representations, emotion regulation, and extinction all involve specific sectors of the prefrontal cortex. The PFC, along with the insula, is important for our conscious experience of emotions (Salzman & Adolphs, 2021). [In behavioral learning, extinction refers to the gradual weakening and eventual disappearance of a conditioned response when the reinforcement that initially supported it is no longer provided].
SUBREGIONS OF THE PFC AND THEIR ROLES IN EMOTIONAL PROCESSING:
---- Dorsolateral Prefrontal Cortex (DLPFC): Involved in the regulation of emotions, working memory, and executive functions.
---- Orbitofrontal Cortex (OFC): Evaluates immediate rewards and punishments, predicts outcomes, integrates sensory information with emotions. Key in decision-making based on immediate reward evaluations and in social interactions.
---- Ventromedial Prefrontal Cortex (vmPFC): Regulates emotions, assesses long-term value of choices, involved in self-awareness and empathy. Critical for long-term decision-making, emotional stability, and social cognition. The vmPFC is connected with the amygdala (Note: the OFC and vmPFC are anatomically and functionally overlapping but distinct).
---- Frontal Pole: Integrates sensory and memory inputs, supports self-reflection, and forms complex mental models to generate conscious emotional experiences. Key in higher-order cognitive processes and emotional regulation.
