Motivation and emotion/Book/2014/Amygdala and emotion

Overview

What is the amygdala? What does the amygdala do? How is the amgydala related to emotion? This book chapter is aimed at using research knowledge and emotion theory to answer these questions which in turn will assist the community to understand and improve their lives.

To understand how the amygdala relates to emotion it is first important to have an understanding of what the amygdala is, where it is located, and what the roles of the amygdala are. Not only is it important to understand what the amygdala is but it is also important to know what an emotion is. The following paragraphs will explain both before delving into the more specific roles the amygdala plays within emotion and how they interact with each other using psychological and biomedical research.

What is the amygdala?

Figure 1. The Amygdala is shown in red

Amydale is the Greek word for almond, and eidos is the Greek word for like; therefore the translation would be 'like an almond' (Healthline, 2014). The amygdaloid body (amygdala) is a small almond shaped structure made up of nuclei which is apart of the limbic system (Bailey, 2014). The amygaloid body was named as such because of its almond shape (Healthline, 2014). The amygdaloid body is also known as the amygdale, nucleus amygdalae, porpus amygdalolieum, amygdaloid complex, and amygdaloid nucleus (Healthline, 2014). The most common name is the amygdala.

The amygdala can be located deep within the temporal lobe of the brain (Bailey, 2014). Specifically it is associated with the hypothalamus, cingulated gyrus, and hippocampus (Healthline, 2014). A concrete definition of the roles of the amygdala has not yet been established, nor has exact functions been allocated to each of its subgroups (Holt, 2008). There has been much debate on how many subgroups there are within the amygdala resulting in categories between 5 and 22 (Holt, 2008). On the other hand there are four main groups that have been universally agreed upon which are the Basolateral, Lateral, Central and Basomedial Nuclei (Holt, 2008).

Smelling, motivation, and emotional responses are made by the olfactory system and the limbic system and are partly made by the amygdaloid body (Healthline, 2014). The amygdala is central to our emotions and motivations, especially emotions related to survival (Bailey, 2014). The amygdala's function is to process emotions such as fear, anger and anxiety (Bailey, 2014). The amygdala is also essential for determining what memories are stored and where memories are stored within the brain (Bailey, 2014). It has been suggested that the decision as to where the memory is stored is based on how huge an emotional response a particular event invokes (Bailey, 2014).

What is an emotion?

Figure 2. Emotion Mosaic

Emotions tend to occur as reactions to important life events (Reeve, 2009). Emotions consist of four main elements- feeling, arousal, purpose and expression (Reeve, 2009). Feelings give emotions subjective personal meaning (Reeve, 2009). Arousal is the biological activity that prepares the body for adaptive coping behaviour (Reeve, 2009). Purpose gives an emotion goal-direction and motivation to take a certain course of action (Reeve, 2009). Expression gives emotion a social aspect which is important for communication with others (Reeve, 2009). Emotion is therefore defined as a psychological construct which unifies and coordinates these four elements of experience to create an orchestrated and adaptive pattern (Reeve, 2009).

Fear and the amygdala

The pathways which allow us to both consciously and subconsciously interpret fear is still not understood by neuroscientists (Bergland, 2013). However the amygdala has been proven to be involved in various aspects of fear processing (Feinstein, Adolphs, Dasmasio & Tranel, 2011). This includes fear conditioning, modulation of attention and memory for fear-related stimuli, fear recognition, and the induction of fear-related behaviours (Feinstein et al., 2011). These are all subconscious aspects of fear. Not alot is known about the amygdala's role in conscious experiences of fear due to the fact that nonhuman animals with lesions lack the ability to verbally report on their internal subjective experience (Feinstein et al., 2011). The second reason is that humans with focal bilateral amygdala damage are extremely difficult to find (Feinstein et al., 2011).

The amygdala's role in fear conditioning

Figure 3. Pavlov famous for Classical Conditioning

Fears can be either innate or learned. Innate fears are defined as any fear that has been encoded within our genes. Learned fears are acquired through painful or traumatic life experiences. A majority of what is known about learned fear is from Pavlovian fear conditioning (Erlich, 2006). Fear conditioning is a form of classical conditioning where both humans and animals learn to fear specific objects or situations (Layton, 2014). The amygdala is an essential component in the neural circuit underlying fear conditioning (Erlich, 2006). For example the four main nuclei which are important for auditory fear conditioning are the lateral, central, basal, and intercalated nuclei (Elrich 2006). Each of these nuclei play a specific part in fear conditioning (Elrich, 2006). The lateral nucleus is the accepted area of learning where the CS and the US input form together to create the CS-US association (Elrich, 2006). The central nucleus is important for automatic reactions to fear such as freezing (Elrich, 2006). The intercalated area is suggested to be a gateway between the lateral nuclei and the central and has been proposed to be the component responsible for the regulation of fear (Elrich, 2006). Lastly, the basal nucleus is said to be necessary for the active responses to the CS such as the act of escaping a certain situation (Elrich, 2006).

The fight or flight response

The fight or flight response is the body’s reaction to acute stress which prepares the body to either flee or fight a threat (Cherry, 2014). This threat can be either real or imaginary (Cherry, 2014). When an animal experiences a stressful event the amygdala is the area of the brain responsible for sending a distress signal through to the hypothalamus (Harvard University, 2014). The hypothalamus then activates the sympathetic nervous system by sending messages through the autonomic nerves to the adrenal glands (Harvard University, 2014). The adrenal glands respond by pumping the hormone epinephrine (commonly known as adrenaline) into the bloodstream (Harvard University, 2014). The adrenaline causes all kinds of physiological responses to occur which happen so rapidly that people aren't aware of them (Harvard University, 2014). The wiring is so efficient that the amygdala and hypothalamus start this train of events even before the brain's visual centres have had a chance to fully process what is happening (Harvard University, 2014).

The amygdala is the brain's radar for threat (Goleman, 2011). If it detects a threat the amygdala has the ability to take control of the entirety of the brain (Goleman, 2011). This occurrence is more commonly known as an amygdala hijack (Goleman, 2011). To put it simply when this happens the person is no longer able to concentrate on anything else other than the perceived threat (Goleman, 2011). The person then relies on habitual behaviour and is no longer able to learn, innovate or be flexible (Goleman, 2011). This phenomena is referred to as the fight-flight-freeze response (Goleman, 2011). The main problem with this is that the amygdala can often make mistakes (Goleman, 2011). For example the amygdala will only retrieve some of the data in which the senses have picked up rather than accepting the entire picture of what is happening (Goleman, 2011). Because of this non complete picture the amygdala can often act instantly causing the person to overreact toward the situation (Goleman, 2011).

The amygdala's role in anxiety disorders

Post-traumatic stress disorder (PTSD)

What is post-traumatic stress disorder (PTSD)?

PTSD is an anxiety disorder which develops after an individual has lived through a traumatic event. This traumatic event would have caused that person to feel as if their life or their love ones lives were in danger. Individuals with PTSD frequently display significant distress that they would have felt during the traumatic event (BeyondBlue, 2014).

The amygdala's role in PTSD:

Research has shown that there is a connection between the amygdala and Post Traumatic Stress Disorder (PTSD) (Smith, Abou-Khalil, & Zald, 2008; Ruden, 2010; Dębiec, 2011). For example Smith, Abou-Khalil, & Zald (2008) conducted research on the link between the amygdala and the development of PTSD. They conducted a case study using a patient with PTSD who had their left amygdala removed after a car accident (Smith et al., 2008). They found that the right amygdala was responsible for some of the processes that assist the body in the expression of PTSD (Smith et al., 2008). They concluded that a person is still capable of presenting with PTSD even within the absence of the left amygdala (Smtih et al., 2008). These findings are supported by Dębiec (2011) who used stimulation of the amygdala of PTSD patients to find out whether the stimulation would increase the likelihood of reconsolidation of fear memories. Dębiec (2011) suggested that reconsolidation may be useful in understanding PTSD and by extension increase understanding of how to treat PTSD.

Antisocial personality disorder

What is antisocial personality disorder?

Anti-social personality disorder (Diagnostic and Statistical Manual Fifth Edition; DSM V) is characterized by an individual displaying consistent disregard for other individual's rights and often violating these rights (PsychCentral, 2014). Antisocial Personality Disorder is also referred to as psychopathy and sociopathy, however these terms are not used for professional diagnosis nor are they mentioned within the DSM V (PsychCentral, 2014). People with anti-social personality disorder often lack empathy and tend to be cold and cynical (PsychCentral, 2014). They also disregard the feelings, rights, and sufferings of others as well as being excessively opinionated, self-assured and demonstrates arrogant self-appraisal (PsychCentral, 2014). A personality disorder is a consistent, long lasting pattern of inner experience and behaviour that deviates from the norm of the individual’s culture (PsychCentral, 2014).

The amygdala's role in antisocial personality disorder:

Research has demonstrated that there is a connection between the amygdala and Anti-social Personality Disorder (Gao, 2009; Marsh, 2013). Goa (2009) found that defects within the amygdala-hippocampal complex have been associated with emotional defects such as shallowness, lack of remorse, pathological lying and superficial charm that are present within people with anti-social Personality Disorder. These findings were later supported by Marsh (2013) who examined youthful individuals with psychopathic traits. Marsh (2013) demonstrated that those with psychopathic traits had low activity within the amygdala which in turn is associated with empathic pain as the displayed pain increased. This reduction within the amygdala was at its lowest when the injury was happening to someone else (Marsh, 2013).

Phobias

What is a phobia?

According to the American Psychiatric Association a phobia is defined as an anxiety disorder which causes the person to have irrational and excessive fear of a certain situation or object (Cherry, 2014). This fear is so extreme that the individual with go to great lengths to avoid what is causing them to feel the fear, often disrupting day-to-day life (Medical News Today, 2014). If confronted with the certain situation or object it will cause the individual significant distress, so much so that it interferes with their normal functioning (Medical News Today, 2014). The two main categories of phobias are as follows:

Specific phobias (also known as Simple Phobias) that involve a disproportionate fear about specific situations, living creatures, places, activities, or things (Medical News Today, 2014). Some examples of specific phobias are as follows:

Dentists (dentophobia)
Snakes (opidiophobia)
Birds (ornithophobia)

Complex phobias which are linked to a deep-rooted fear or anxiety about certain situations, incidents or circumstances (Medical News Today, 2014). These complex phobias are called as such due to these phobias being a great deal more disabling than the simple phobias (Medical News Today, 2014). The two main categories of complex phobias are as follows:

Social anxiety disorder: finding social situations extremely uncomfortable and possibly even unbearable e.g. party or wedding (Medical News Today, 2014).
Agoraphobia: fear of finding ones self in a situation where one cannot escape e.g. lifts or small rooms (Medical News Today, 2014).

The amygdala's role in phobias

Research has found that the amygdala plays a role in phobias by examining abnormalities in the volume, shape and activation of the amygdala (Lipka, Miltner, & Straube 2011; Fisler, Federspiel, Horn, Dierks, Schmitt, Wiest, De Quervain, & Soravia, 2014; Burklund, Craske, Taylor, & Lieberman, 2014). Lipka et al. (2011) examined the activation of the amygdala in those who had a specific phobia (spiders), finding that the patients showed stronger responses of both amygdalae to consciously perceived spiders. Whereas during unconscious stimulus processing, enhanced activation was present only within the right amygdala (Lipka et al., 2011). These findings were later supported by Fisler et al.[grammar?] (2014) finding that a spider phobia might be characterized by a deregulation in both an initial amplified fear response during exposure to spiders as well as a subsequent impaired down-regulation of the elicited fear response.

The amygdala (among other parts of the brain) has been found to be responsible for the storage and retrieval of dangerous or potentially dangerous memories of situations and events (Medical News Today, 2014). Should an individual be in the same or similar situation they were in before, the amygdala retrieves that same memory resulting in the rest of the body reacting in much the same way as it had the last time this occurred (Medical News Today, 2014). Depending on the individual it may feel as if the person is going through the event several times rather than just once (Medical News Today, 2014).

The recognition and regulation of emotions

Emotion recognition

One of the first social skills humans learn as infants is the ability to recognize emotions. The expressions of others can assist us to recognize the emotions and even the intentions of others (Cristinzio, Sander, & Vuilleumier, 2007). Having difficulty recognizing emotional expressions can occur after neurological diseases, which indicates that the human brain has inbuilt circuits for discriminating facial expressions (Cristinzio et al., 2007). In particular, the amygdala has been demonstrated as being a key aspect in emotional face processing (Pessoa, & Adolphs, 2010; Hooker, Bruce, Fisher, Verosky, Miyakawa, D’Esposito, & Vinogradov, 2013). Pessoa & Adolphs (2010) evaluated the significance of the amygdala in processing emotional visual stimuli and how emotional visual stimuli is processed throughout the brain. They proposed that the amygdala's role within the processing of emotional stimuli is to coordinate the function of cortical networks (Pessoa & Adolphs, 2010). Hooker et al. (2013) supported these findings showing that the amygdala is more activated during facial recognition than face identity or other face judgments. They also demonstrated that those with schizophrenia tend to have low activation within the amygdala during emotion recognition (Hooker et al., 2013). They did occasionally find individuals with schizophrenia showing high rates of activation during emotion recognition (Hooker et al., 2013). However, they suggested that this was simply due to misinterpretation of emotional stimuli rather than accurate emotion recognition (Hooker et al., 2013).

Universal facial expressions of emotion

The first person to suggest that facial expressions of emotion was universal was Charles Darwin (Matsumoto & Hwang, 2011). Charles Darwin proposed that facial expressions of emotion were biologically innate and evolutionarily adaptive (Matsumoto & Hwang, 2011). Tomkins later added to this suggesting that emotion was the basis of human motivation and found evidence that facial expressions were associated with certain emotional states (Matsumoto & Hwang, 2011). Additionally Tomkins, Ekman and Izard later conducted what is commonly known as 'the universal studies' proving that emotional facial expressions were the same in both literate and preliterate cultures (Matsumoto & Hwang, 2011). They also found that people across cultures were in high agreement in judgments of emotions in faces from both literate and preliterate cultures (Matsumoto & Hwang, 2011). Many researchers have since replicated these studies and found overwhelming evidence in support for the universal facial expression of seven emotions - anger, contempt, disgust, fear, joy, sadness, and surprise (Matsumoto & Hwang, 2011).

Microexpressions

Microexpressions are likely signs of concealed emotions (Matsumoto & Hwang, 2011). Microexpressions are expressions that happen so fast that people are often unaware that they even occurred at all (Matsumoto & Hwang, 2011). Darwin (1872) suggested that facial actions that cannot be controlled voluntarily may be produced involuntarily even if the individual is trying to control his or her expressions (Matsumoto & Hwang, 2011). The existence of microexpressions was confirmed by Haggard & Issac (1966) while they were scanning films in slow motion (Matsumoto & Hwang, 2011). This was later supported by Ekman and Friesen (1974) and most recently by Porter and Brinke (2008) who demonstrated that microexpressions occurred when individuals were attempting to be deceitful about their emotional expressions (Matsumoto & Hwang, 2011).

Emotion regulation

Emotion regulation is an individual's ability to understand and accept his or her emotional experience, to actively participate in healthy strategies to manage uncomfortable emotional experiences, and to display appropriate behaviour when distressed (Salters-Pedneault, 2014). Research has shown that the amygdala plays a role in emotion regulation (Banks, Eddy, Angstadt, Nathan, & Phan, 2007; Gross, 2011; Lee, Heller, Reekum, Nelson, & Davidson, 2012). Lee et al. (2012) demonstrated that the greater the coordination between the amygdala and the prefrontal cortex the better the individual was able to down-regulate negative emotion. Down-regulation is the process of decreasing a number of receptors for a chemical on cell surfaces in a certain area, usually due to long-term exposure to the agent (Farlex, 2014). Therefore the amygdala plays an important role in emotion regulation by playing a part in an individual's ability to down-regulate negative emotion.

Ways to improve your emotion regulation

Figure 4. Cat expressing joy

Identify and label specific emotions that you are feeling - What prompted the emotion? What is happening in your body? How did you feel about the event? What behaviour(s) you were expressing?
Be proactive and seek balance - balance healthy eating, sleep, exercise, staying away from mood altering drugs etc.
Increase positive experiences - do things that you enjoy doing
Change your behaviour - for example when you are angry do not yell stay quiet and walk away from the situation that is causing the anger
Stay mindful - be aware that experiencing emotions is a part of normal human life

Aggression and the amygdala

Aggression within society has become an increasingly important area of study within the psychological and biomedical communities. Aggression within the psychological community can be defined as any behaviour that results in the physical or psychological harm to oneself, another or objects within the environment (Cherry, 2014). The expression of aggression can form in a variety of ways such as verbally, mentally and physically (Cherry, 2014). There are two main forms of aggression and they are premeditated aggression and impulsive aggression (Damasio, 2007). Premeditated aggression is when a person plans to be aggressive before the situation takes place hence the name 'premeditated' aggression (Damasio, 2007). Impulsive aggression is mostly unplanned and spontaneous acts of aggressive behaviour (Damasio, 2007).

Research has demonstrated that the amygdala plays a role in aggression. Matthies, Rusch, Weber, Lieb, Philipsen,Tuecher, Ebert, Hennig, and Van Elst (2012) showed by using morphometric brain imaging and amygdala measurements that the amygdala's volume was connected to how much aggression any given individual would display. They found that individuals with higher aggression scores showed roughly a 16-18% reduction of amygdala volumes (Matthies et al., 2012). They suggested that amygdala volumes may be an important marker for indicating aggressiveness within mentally healthy human beings (Matthies et al., 2012). Passamonti, Crockett, Apergis-Schoute, Clark, Rowe, Calder, and Robbins (2012) supported these findings that the amygdala is responsible for emotions such as aggression when they conducted research using serotonin. Passamonti et al. (2012) conducted research on whether ATD would affect functional connectivity in neural networks involved in processing social signals of aggression (e.g., angry faces). Passamonti et al. (2012) showed that ATD significantly modulated the connectivity between the amygdala and two PFC regions (ventral anterior, cingulate cortex, and ventrolateral PFC) when processing angry vs. neutral and angry vs. sad but not sad vs. neutral faces. They also showed that serotonin depletion reduced the influence of processing angry vs. neutral faces on circuits within PFC and on PFC–amygdala pathways (Passamonti et al., 2012). They concluded that serotonin significantly influences PFC–amygdala circuits implicated in aggression and other affective behaviors (Passamonti et al., 2012).

Emotional memories

Figure 5. The Hippocampus is shown in red

Emotionally arousing and stressful experiences are retained within memory and it has been long known that the amygdala plays a substantial role in this process (Hermans, Battaglia, Atsak, de Voogd, Fernandez, & Roozendaal, 2014). This notion dates back to the report by Kluver and Bucy (1937) who demonstrated the effects of temporal lobectomy in rhesus monkeys (Hermans et al., 2014). Bilateral lesions of this area where demonstrated to result in striking behavioural changes such as alterations in affective behaviours, including loss of fear (Hermans et al., 2014). However, beneficial effects of emotional arousal extended beyond fear learning (Hermans et al., 2014). During an emotionally arousing period, stress hormones (epinephrine and glucocorticoids) are released from the adrenal glands and numerious neurotransmitters and neuropeptides are released in the brain (Hermans et al, 2014). The amygdala plays an essential role in combining together these various influences on memory (Hermans et al, 2014). The modulation hypothesis suggested that during and shortly after an emotionally arousing experience, the amygdala uses stress-related hormones and neurotransmitters to enhance the consolidation and storage of memory within other areas of the brain (Hermans et al., 2014).

The amygdala and the hippocampus are both major structures within the temporal lobe that are linked to two independent memory systems (Phelps, 2004). However when people are in emotional situations these two separate systems interact (Phelps, 2004).The amygdala both encodes and stores the hippocampal-dependent memories (Phelps, 2004). The hippocampus can influence the amygdala's response when emotional stimuli is presented (Phelps, 2004). These findings have been supported by Paz & Pare (2013) stating that in emotionally arousing situations, whether they are positive and negative, the amygdala allows incoming information to be processed more efficiently in distributed cerebral networks. Hermans et al. (2014) further supported these findings stating that the amygdala activation enhances memory consolidation by facilitating neural plasticity and information storage processes in its target regions.

Conclusion

The amygdala is an almond shaped structure located in the limbic system within the brain. The amygdala plays a number of roles within emotion such as processing emotions such as aggression, anxiety and fear. The amygdala also plays an important role in the storage and retrieval of emotional memories. The amygdala is responsible for processing fear which includes includes the modulation of attention and memory for fear-related stimuli, fear recognition, the induction of fear-related behaviours, and fear conditioning. The amygdala also plays an important role within the fight or flight response. Research has proven the association between abnormalities in the amygdala and the presence of anxiety disorders which include PTSD, antisocial personality disorder and phobias. Research has also proven an association between activation within the amygdala and emotional facial recognition as well as emotional regulation. On top of that research has proven an association between the amygdala and aggression through the examination of serotonin levels and amygdala volume. Lastly, the amygdala encodes, stores and retrieves emotional memories.

Test your memory

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	Lateral, Prefrontal, Basomedial, and Central
	Basolateral, Lateral, Central and Basomedial nuclei
	Amygdaloid Body, Lateral, Central and Prefrontal
	Basomedial, Lateral, Central, and Prefrontal

	Overt fears that cannot be observed
	Fears that are learnt through experience
	Fears that are observable
	Any fear that has been encoded within our genes

	to down-regulate negative emotion
	to over-regulate positive emotion
	to over-regulate negative emotion
	to down-regulate positive emotion