How does emotion work? - Chapter 10

People have been struggling to define emotion for several thousand years. As a psychological state, emotion has some unique qualities that have to be taken into account. Emotions are embodied, you feel them. They are uniquely recognizable; they are associated with characteristic facial expressions and behavioral patterns of comportment and arousal. Emotions are neurological processes that have evolved to guide behavior in such a manner as to increase survival and reproduction. They improve our ability to learn from the environment and the past. Many researchers claim that a feeling is the subjective experience of the emotion, but not the emotion itself. The most current models posit that emotions are valenced responses (positive/negative) to external stimuli and/or internal mental representations that

• involve changes across multiple response systems

• are distinct from moods, in that they often have identifiable objects or triggers

• can be either unlearned responses to stimuli with intrinsic affective properties, or learned responses to stimuli with acquired emotional value

• can involve multiple types of appraisal processes that assess the significance of stimuli to current goals

• depend of different neural systems

Others agree that emotions involve highly coordinated behavior, body and brain effects, they disagree that these various effects are part of the emotion state. They view them as a result or consequence of the emotion state

• an 'emotion' constitutes an internal, central state

• this state is triggered by specific stimuli

• this state is encoded by the activity of particular neural circuits

• activation of these specific circuits gives rise, in a causal sense, to externally observable behaviors, and to separately associated cognitive, somatic and physiological responses

Emotions fall under the umbrella term of affect, which includes not only discrete emotions that have a relatively short duration, but also more diffuse, longer-lasting states such as chronic stress and mood. Encountering a stimulus or event that threatens us in some way triggers stress, a fixed pattern of physiological and neurohormonal changes. These changes disrupt homeostasis, leading to immediate activation of the sympathetic nervous system's fight-or-flight responses, but also to activation of the hypothalamic-pituitary-adrenal axis and release of stress hormones, such as cortisol. 

A mood is a long-lasting diffuse affective state that is characterized by primarily a predominance of enduring subjective feelings without an identifiable object or trigger. Moods do not have a well-defined neurohormonal or physiological substrate, and the neural correlates of different moods are still poorly understood. 

What are the neural systems that are involved in emotion processing?

The identifying of the neural systems involved in emotion processing is difficult: technical issues with the various methods used to study emotion, controversies over whether emotional feeling, which are subjective, can be studied in humans and animals, and the various interpretations of research findings. 

When emotions are triggered by an external event or stimulus, our sensory system plays a role. The autonome nervous system, or ANS ,is made up of the parasympathetic and sympathetic nervous systems. The two systems work in combination to achieve homeostasis. The ANS is regulated by the hypothalamus, which also control the release of multiple hormones through the HPA axis, made up of the paraventricular nucleus (PVN) of the hypothalamus, the anterior lobe of the pituitary gland, and the cortex of the adrenal glands, which sit above the kidney. Arousal is a critical part of many theories of emotion. The arousal system is regulated by the reticular activating system, which is composed of sets of neurons running from the brainstem to the cortex. 

Papez came up with a circuit that has to do with emotion. The Papez circuit describes the brain areas that James Papez believed were involved in emotion. They include the hypothalamus, anterior thalamus, cingulate gyrus, and hippocampus. The limbic system includes these structures and the amygdala, orbitofrontal cortex, and the portions of the basal ganglia. MacLean proposed that the human brain had three regions that had developed gradually and sequentially over the course of evolution. He used the term limbic system to describe the complex neural circuits involved with the processing of emotion. 

Over the last decades, scientific investigation of emotion has been focused more on human emotion and has also became more detailed and complex. Investigators no longer think there is only one neural circuit of emotion. Rather, depending on the emotional task or situation, we can expect different neural systems to be involved. The neuroimaging approaches based on machine learning revealed that specific emotional states activate several brain networks. 

How do you categorize emotions?

In this section we discuss the basic versus dimensional categorization of emotions. Fearful, sad, anxious, elated, etc. are some of the terms we use to describe our emotional lives. Researchers made up three primary categories:

1. Basic emotions: a closed set of emotions, each with unique characteristics, carved by evolution and reflected through facial expressions

2. Complex emotions: combincations of basic emotions, some of which may be socially or culturally learned, that can be identified as evolved, long lasting feelings

3. Dimensional theories of emotion describe emotions that are fundamentally the same but that differ along one or more dimensions, such as valence and arousal, in reaction to events or stimuli

What are the basic emotions?

There are seven primary-process emotional systems, or core emotional systems, produced by ancient subcortical neural circuits common to all higher animals, which generate both emotional actions and specific autonomic changes that support those actions: SEEKING/desire, RAGE/anger, FEAR/anxiety, LUST/sex, CARE/maternal, GRIEF/seperation distress and PLAY/physiological social engagement. 

For the past 150 years, many investigators of human emotions have considered facial expressions to be one of those predictable changes sparked by an emotional stimulus. Duchenne was the first in doing experiments with facial expressions in a man with facial anesthesia. He electrically stimulated the man's facial muscles and methodically triggered muscle contractions. Duchenne believed that facial expression revealed the underlying emotions. Ekman took up this work and the study of facial expression and came up with the six basic human facial expressions: anger, fear, sadness, happiness, disgust and surprise. Some of the basic emotions have been confirmed in nonhuman mammals, which show dedicated subcortical circuitry for such emotions. 

What are the complex emotions?

Even if we accept that the basic emotions exist, we are still faced with identifying which emotions are basic and which are complex. Jealousy is one of the most interesting of the complex emotions. Also, romantic love is far more complicated than researchers initially thought. These emotions are associated with higher-order cortical areas and are involved with social cognition, theory of mind, and interpretation of actions performed by others. 

Most researchers agree that emotional reactions to stimuli and events can be characterized by two factors: valence (positive and negative) and arousal (high or low). Although, sometimes it is the case that a person feels positive and negative at the same time. By using the dimensional approach - tracking valence and arousal - researchers can be more concretely in assessing emotional reactions elicited by stimuli. So, the dimensional approach, instead of describing discrete states of emotion, describes emotions as reactions that vary along a continuum. 

What are the theories of emotion generation?

Most emotion researchers agree that the response to emotional stimuli is adaptive and that it can be separated into three components. Every theory of emotion generation is an attempt to explain:

• The physiological reaction (racing heart)

• The behavioral reaction (fight-or-flight response)

• The subjective experiential feeling ('I'm scared!')

What the theories don't agree on are the underlying mechanisms, and what causes what. The crux of the disagreement involves the timing of these three components and whether cognition is required to generate an emotional response and subjective feeling or, alternatively, whether an emotional stimulus leads directly to quick automatic processing that results in a characteristic response and feeling.

James-Lange theory of emotion:

James proposed that emotions were the perceptual results of somatovisceral feedback from bodily responses to an emotion-provoking stimulus. A sense organ relayed information about that stimulus to the cortex, which then sent this information to the muscles and viscera. The muscles and viscere than react by sending information back to the cortex, and the stimulus that had simply been apprehended has now emotionally felt. 

Thus, when you run away because you see a bear and you're scared of bears, in the James's view, you don't run because you are afraid, you run first and you are afraid later, because you become aware of your body's physiological changes when you run, and then you cognitively interpret you physical reactions and conclude that what you're feeling is fright. Your emotional reaction depends on how you interpret those physical reactions. Lange went further to test this idea, due the name James-Lange theory. 

Cannon-Bard theory of emotion:

They believed that physiological responses were not distinct enough to distinguish among fear, anger, and sexual attraction, for example. They proposed that we simultaneously experience emotions and physiological reactions: the thalamus processes the emotional stimuli and sends this information simultaneously to the neocortex and to the hypothalamus, which produces peripheral response. The Cannon-Bard theory remains important because it showed that reactions to emotional stimuli could occur without the cortex, at least in nonhuman animals. 

Appraisal theory of emotion:

The Appraisal theory is a group of theories that say that emotion processing depends on an interaction between the stimulus properties and their interpretation. The theories differ about what is appraised and the criteria used for this appraisal. Lazarus proposed a version of appraisal theory in which emotions are a response to the reckoning of the ratio of harm versus benefit in a person's encounter with something. Thus, the cause of emotion is both the stimulus and its significance. Cognitive appraisal comes before emotional response or feeling, this appraisal step may be automatic and unconscious. 

Singer-Schachter theory: cognitive interpretation and arousal

Singer and Schachter agreed with James and Lange that the perception of the body's reaction was the emotion, but they also agreed with Cannon and Bard that there were too many emotions for there to be a specific and unique autonomic pattern for each. The theory proposes that emotional arousal and then reasoning are required to appraise a stimulus before the emotion can be identified. 

LeDoux's fast and slow roads to emotion:

LeDoux has proposed that humans have two emotion systems operating in parallel. One is a neural system for our emotional responses that bypasses the cortex and was hardwired by evolution to produce fast responses that increase our chances of survival and reproduction. The other system, which includes cognition, is slower and more accurate, this system generates the conscious feeling of emotion. Brain circuits that detect and respond to threats should be referred to as defensive circuits, and behaviors that occur in response to threats should be referred to as defensive behaviors. 

Evolutionary psychology approach to emotion:

They suggest that emotions can be an overarching program that directs the cognitive subprograms and their interactions. An emotion is not reducible to its effects on physiology, behavioral inclinations, cognitive appraisal, or feeling states, because it involves coordinated, evolved instructions for all of these aspects together. 

Panksepp's hierarchical-processing theory of emotion:

He hypothesized that emotions are subject to a control system with hierarchical processing. Emotion is processed in one of three ways; the most basic are the basic emotions and these arise straight from the neural networks in the subcortex. Cognition plays no further role when it comes to feeling these emotions. The core emotions arise from conditioning, and the tertiary-process emotions are elaborated by cognition. 

What is the amygdala?

The amygdala is a small, almond-shaped structure in the medial temporal lobe adjacent to the anterior portion of the hippocampus. It is a collection of 13 nuclei that can be grouped into three main amygdaloid complexes: basolateral nuclear complex, centromedial complex and the cortical nucleus. The amygdala is known for that it is the most connected structure in the forebrain in humans. It has receptors for many different neurotransmitters and for various hormones that are present in the brain. 

What is the influence of emotion on learning?

Claparède was the first to provide evidence that two types of learning, implicit and explicit, are apparently associated with two different pathways. He was a doctor who had a client with Korsakoff's syndrome. Every morning he had a ritual of shaking the hands of the clients he met. On a day he put a pin needle in his hand when he shaked hers. The next morning she, of course, didn't remember who the doctor was but as soon as he extended his hand to greet her, she hesitated for the first time. Implicit learning is a type of Pavlovian learning in which a neutral stimulus acquires aversive properties when paired with an aversive event. This is a classic example of fear conditioning. There is also a phenomenon called extinction; it represents new learning about the stimulus that inhibits expression of the original memory. 

The amygdala is necessary for implicit learning, but it is not necessary for explicit or emotional learning. The conscious knowledge of an upcoming shock (in for instance an experiment of conditioning) cannot generate physiological changes normally associated with fear if there is no link present to link it to the amygdala and its midbrain connections. Information can come to the amygdala via two separate pathways; the 'low' road - goes directly from the thalamus to the amygdala, and the 'high' road - goes from the cortex to the amygdala. 

Next to the amygdala is the hippocampus (in the state of learning) only necessary for the acquisition of a memory, but if arousal accompanies memory acquisition the strength and duration of that memory is modulated by amygdala activity. 

What are the interactions between emotion and other cognitive processes?

Much research has been focused on the effects of emotion on learning and memory, its effects on other cognitive processes are also being unraveled. 

We have a increased awareness for and pay attention to emotionally salient stimuli. Researchers often use the paradigm of the attentional blink to test this, in which stimuli are presented so quickly in succession that an individual stimulus is difficult to identify. But if participants are told to disregard all the other words, they are able to identify the targets. The proposed mechanism for this attentional change is that early in the perceptual processing of the stimulus, the amygdala receives input about its emotional significance, and, through projections to sensory cortical regions, modulates the attentional and perceptual processes. Fearful stimuli are not the only stimuli processed by the amygdala, especially fearful and disgusting ones have the priority. 

The amygdala is critical in bringing an unattended but emotional stimulus into the realm of conscious awareness by providing some feedback to the primary sensory cortices, thus affecting perceptual processing. 

A popular idea is that emotion leads people to make suboptimal and sometimes irrational decisions. The hypothesis that emotion and reason are separable in the brain and compete for control of behavior is often called 'dual-systems theory' and it has dominated Western thought since Plato. But the dualism theory has not been substantiated. Our current understanding suggests that there are two ways by which emotion influences decision making:

1. Incidental affect: current emotional state, unrelated to the decision at hand, incidentally influences the decision

2. Integral emotion: emotions elicited by the choice options are incorporated into the decision. This process may include emotions that you anticipate feeling after you have made the decision, which humans are notoriously bad at predicting.

What is the link between emotion and social stimuli?

Studies have shown that there is an dissociation between identifying an individual's face and recognizing the emotional expression on that face. Neuroimaging in normal patients and patients with anxiety disorders have reported that increased amygdala activation in response to brief representations of faces with fearful expressions are higher compared to faces with neutral expressions. The amygdala response/activation is significantly greater when in response to fear. One interesting part is that the participant does not need to be aware of the fearful face for the amygdala to respond. People who have extensive damage to the amygdala are not able to recognize fearful or untrustworthy facial expression. 

What are other important areas or emotions?

The insula is tucked between the frontal and temporal lobes in the Sylvian fissure. It has reciprocal connections with areas associated with emotion, such as the amygdala, medial prefrontal cortex, and anterior cingulate gyrus. There is a significant correlation between the insular activity and the perception of internal bodily states, known as interoception. The connections and activation profile of the insula suggest that is integrates visceral and somatic input and forms a representation of the state of the body. 

Depending on how the information is analyzed, different neuroimaging studies have been interpreted to both support and refute the theory that there are different brain areas or circuits associated with the processing of different emotions. 

How does the cognitive control of emotion work?

Emotion regulation refers to the processes that influence the types of emotions we have, when we have them, and how we express and experience them. Emotion regulation processes can intervene at multiple points during the generation of emotion, some early on and some after the fact. Researchers investigate how we regulate emotion proceed by changing the input or the output. Change to the input can consist of avoiding the stimulus altogether, or altering the emotional impact of the stimulus by reappraisal. There is also a phenomenon, suppression, where the response to a emotional stimulus is altered a certain way. It reinterprets an emotion-laden stimulus in non-emotional terms. Research shows that reappraisal can lead to reduced emotional experience, suppression on the other hand caused participants to be more aroused.