Motivation and emotion/Book/2023/Interoception and mental health

Overview


How do you know if you’re feeling frightened? Do you feel your heart rate increase? Do your hands begin to tremble? Maybe, you begin to have trouble breathing. These bodily functions are our undercover, interoceptive senses that help to ensure the maintenance of our wellbeing.

Interoception refers to the process where the body communicates its internal state through bodily signals via the nervous system. These processes are a way to maintain homeostasis across all major biological systems (see Figure 2) and motivate us to act on these signals. When the body’s set-point of homeostasis is unstable, it helps people become aware of this through interoceptive processes such as breath quickening, increased heart rate, hunger cues and bladder fullness. If these processes are not working as they should, interoception make this known through things like nausea and pain (Weir, 2023).

When bodily processes are in communication with our brain, interoceptive processes are brought into conscious awareness – this is known as interoceptive awareness. Once in conscious awareness, the brain uses attention, learning, memory, emotion and cognition to ensure the body maintains its homeostatic state (Berntson and Khalsa 2021). For example, the brain knows the feeling of a full bladder means it needs to be emptied, so it will motivate us to go to the toilet. Because this phenomenon has effects on so many bodily processes, research surrounding this topic is vital. With the help of psychological and biological science, we can begin to explain and treat mental disorders and health issues in new ways.

The relationship between psychology and physiology has long been a point of research. Although interoception is commonly understood in the medical field, it is less understood in the psychology field. Fast growing research has begun to discover a relationship between bodily signals and mental health. The contents of this chapter will begin to explain how exactly these two interrelated, and which theory supports it (Khoury et al., 2018).

James-Lange theory of emotion
This theory attempts to explain what causes emotion. James-Lange (1885) hypothesised that physical change in the body as a result of external stimuli, and the brain’s interpretation of this, leads to the experience of emotion (Cherry, 2022). For example, if you go to the movies and watch a film with a sad scene midway through, you may begin to cry. Your interpretation of this physiological response elicits the emotion of sadness.



Using this theory that emotions are a result of our interpretation of physical reactions to external stimuli, it would help to explain interoception’s role in mental health. If emotions are induced by changing states in the body, then people who are typically perceptive to interoceptive signals will experience ‘normal’ emotional reactions to external stimuli. However, individuals who cannot accurately perceive their interoceptive signals, might fail to experience emotions as they are supposed to (Prinz, 2006).

This theory has been criticised because of its heavy focus on responses that are a large part of the fight-or-flight response in which responses do not change for each emotion (e.g., heart rate, breathing). It is also criticised for its focus on physiological reactions coming before emotional experience – some people argue that emotional experience responds faster than physiological reactions (Reeve, 2018).

So, in the context of interoception and emotion, the question is whether the ability to perceive physiological/interoceptive processes causes emotion or if it is a result of emotional reactions form external stimuli. Modernised approaches to this theory have neglected the significance James-Lange placed on physical arousal causing emotion. It is now believed that emotions trigger physiological responses to adapt to external stimuli. So, according to the revised James-Lange theory of emotion, interoceptive processes may not cause emotion but they are certainly a necessary component of the experience of emotion (Reeve, 2018).

{The James-Lange theory of emotion suggests that: - emotions resulting from external stimuli cause physiological reactions - if you watch a sad movie you will cry + emotions are a result of our interpretation of our physical reactions to external stimuli
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Cannon-Bard theory of emotion


The Cannon-Bard theory of emotion (1927) proposes that we experience emotions and physiological reactions that coincide, simultaneously. In this sense, this theory differs from other theories because both physical and emotional experience rely on one or the other to occur. According to this theory, the thalamus sends a signal to the amygdala and the autonomic nervous system (ANS) that causes a physical reaction in the body (e.g., trembling, sweating). Interoceptive signals are therefore experienced at the same time as an emotion. However, researchers have since criticised the theory for its little emphasis on other areas of the brain that are also responsible for emotion and the physical response (Cherry, 2020).

Schachter and Singer's Two-Factor Theory of Emotion (1962)
Schachter and Singer’s two-factor theory of emotion (1962) describes how emotion occurs under two components. First, the physical arousal that comes from a stimulus, and second, the cognitive label a person puts to the emotion resulting from the stimulus. Essentially, this theory describes that a stimulus causes physical arousal in which the brain uses the environment to associate with an emotion (Mcleod, 2023).

For example:


 * 1) Seeing a bear on a bush walk (stimulus)
 * 2) Feeling your heart race (physical arousal)
 * 3) Noticing that your increased heart rate is due to fear (cognitive label)
 * 4) You become aware that you are frightened (conscious experience of the emotion)

(Cherry, 2019)

According to this theory, the perception of physical arousal (interoception) during a significant event leads to the cognitive label of an emotion, and thus, the conscious experience of that emotion.

How are neurological processes responsible for the interoceptive experience?


Interoceptive signals originate from sensory receptors in the body which relay through the spinal cord and brainstem and into the posterior insular cortex. There are many brain regions responsible for these signals, namely, the insula cortex and cingulate cortex.

The posterior insula cortex is the primary area for interoceptive feelings in the body such as pain, temperature, itches, touch, hunger, thirst, and gustation (taste). The functions of the posterior insula are important as it functions in the subcortical brain and creates unconscious awareness of changes in bodily states (Reeve, 2018).The anterior insula on the other hand, represents these bodily changes through subjective conscious awareness via homeostatic and visceral sensations (e.g., hunger and satiety). It also processes positive and negative emotions towards oneself and others. Thus, those with an anterior insula deficit may have a lack of empathy for others as seen in some mental disorders (Reeve, 2018).

A review by Pasin Neto et al. (2021) also emphasises the importance of the insula cortex and cingulate cortex in interoception and emotion. According to the authors, both the insula and cingulate cortices are activated during emotion. In those with mental disorders, this area is likely to be dysfunctional. Evidence of these area’s activation is shown in imaging reports where subjects experience a variety of feelings including anger, fear, sadness, happiness etc. The anterior insular cortex in particular was activated during all these emotions. This is because it is significantly responsible the integration of physiology and emotion in conscious awareness.

Although the experience of interoception and emotion does occur due to the firing of neurons, modern approaches suggest they are no share a relationship with external stimuli also.

{An example of interoception is: - falling over + cooking a meal when hungry - writing an essay
 * type=""}

{The insula cortex is solely responsible for unconscious awareness of homeostatic and visceral states.} - True + False

How does interoceptive dysregulation affect emotional regulation?
Because interoception studies are relatively recent, it is not yet well known in the psychiatric field. However, neuroscience studies are finding more in-depth conclusions about interoceptive pathways. This helps to integrate recognising bodily sensations into therapeutic interventions to assist both interoceptive dysregulation and mental disorders.

People usually learn labels for internal states through association in their childhood from their caregivers (e.g. being fed when your belly is rumbling). Although interoceptive experiences may fluctuate in adolescence and childhood, some people have reoccurring difficulties when labelling and understanding changing internal states that continues into adulthood. It is still debated whether interoceptive dysregulation causes mental health issues or vice-versa, however, it is likely a bidirectional relationship between the two (Brewer et al., 2021).

Interoceptive dysregulation or interoceptive atypicality is the heightened awareness of bodily sensations, or lack thereof, that attempt to maintain a homeostatic state – both physiologically and emotionally. It is often caused by a hypo-activation or hyper-activation of areas in the brain (often in the insular cortex). The inability to perceive and regulate certain bodily sensations (e.g., heart rate, hunger, reaction to positive stimuli) can exacerbate or stem from mental health issues because of its association with emotional suppression instead of emotional regulation (Brewer et al., 2021). For example, a person’s inability to feel satiated after eating can bring on, or perpetuate, restrictive eating habits as a result of deliberately suppressing interoceptive hunger cues, which leads to decreased interoceptive accuracy (Brewer et al., 2021; Weir, 2023). Interestingly, interoceptive accuracy has also been found to predict better emotional regulation and cognitive reappraisal. However, this is not always a positive trait and can be seen as atypical in some cases and associations with social anxiety, accurate emotional memory (problematic in PTSD), and intense emotional experiences due to one’s heightened sense of internal bodily changes (Brewer et al., 2021).

The link between interoception and emotional regulation is an important topic to better understand ways to improve mental health using interoceptive techniques. Having the ability to regulate interoceptive processes is a core component of rehabilitation in many mental disorders such as anorexia nervosa (Brewer et al., 2021). Higher interoceptive accuracy is thought to improve emotional regulation after negative experiences through identification of useful strategies and cognitive reappraisal (Brewer et al., 2021).

What is the relationship between interoceptive processes and mental health?
Mental health and interoception have a newly researched relationship. The following table (table 1.) provides some of the conscious interoceptive signals that are linked with mental illness.

''Table 1. conscious interoceptive signals that coincide with certain mental illnesses (Khalsa et al., 2018).''

Major depressive disorder


Major depressive disorder (MDD) is a mental illness characterised by (but not limited to) chronic feelings of low positive affect (anhedonia), fatigue, lack of sleep, difficulty concentrating and making decisions, and sometimes thoughts of death or suicide (Torres, 2020).

Interoception maximises experiences of pleasure through informed decision-making as a way to maintain homeostasis. So, in those with MDD, this would imply that their anhedonia is related to decreased interoceptive processes that would typically motivate pleasure-seeking decisions, (Furman et al., 2013). People with MDD have difficulty remembering the feeling of previously enjoyed positive experiences which research suggests is a result of decreased interoceptive abilities (Furman et al., 2013), stemming from a hypo-activation of the insular cortex (Khoury et al., 2018). Without this ability to seek previously pleasurable activities, people with MDD only further sustain their lack of interoception and therefore negative affect.

Anorexia nervosa
Anorexia nervosa (AN) is a serious eating disorder and mental illness. It is the third most common chronic illness among adolescent girls and women and is characterised by an intense fear of gaining weight, restriction of energy intake, and distorted body image (Australia, 2019).

People with AN often have difficulties distinguishing hunger and satiety cues leading as result of poor interoceptive awareness and decreased emotion intensity (Pollatos et al., 2008). Pollatos et al. (2008) conducted a study among females with AN using a heartbeat accuracy test and discovered that they had decreased interoceptive sensitivity compared to healthy control subjects. The authors suggested that this dulled sensitivity to bodily functions is an important factor for onset and perpetuation of psychopathologies. Furthermore, Kerr et al. (2016) discusses that AN patients in their study had abnormal interoceptive activity in their insula which was a contributing factor to subject’s additional anxiety. Interestingly, although AN is known to be associated with a decreased interoceptive awareness of hunger and satiety cues, this study suggests that AN patients may also be hyper-aware of certain gastric sensations in the presence of food due to anticipation of bloating or fullness and subsequently, increasing anxiety (Kerr et al., 2016).

PTSD
Post-traumatic stress disorder (PTSD) is an anxiety disorder characterised by avoidance, hyperarousal, and an impaired ability to change interoceptive states in response to triggering stimuli. Often, people with PTSD have anxiety that stems from anticipation of not being able to properly cope with quickly changing emotional and physical states (Simmons et al., 2009). Research suggests altered activation of the dorso-lateral pre-frontal cortex (DLPFC) and anterior insula in people with PTSD anticipate these interoceptive states and the cognition (anxiety/worry) that comes with this. A disconnection with these areas however has been thought to quicken the physical response to traumatic stimuli and lessen a person’s ability to cope with their response (Simmons et al., 2009). A study conducted by Simmons et al. (2009) discovered subjects had reduced anterior insula and DLPFC activation once being shown aversive stimuli. These subjects therefore lacked both the neural circuitry that prepared the body for physical/emotional/cognitive states, and the ability to distinguish between these bodily states. The study suggested that rather than having decreased interoceptive awareness, subjects more likely had an inability to adapt to interoceptive states.

PTSD specifically, can be applied to any of the three theories of emotion mentioned earlier. James-Lange's theory in particular can help to explain how interceptive processes occur after facing aversive/triggering stimuli. The 'interpretation' stage of this hypothesis is the point in which some people become more aware of their heart rate and breathing. It is based on this interpretation that people with PTSD decide what emotion they are experiencing. For people with increased interoceptive accuracy, this means they are aware of their body's reaction and based previously mentioned research, are actually more likely to regulate its emotions. Those who are less able to interpret their body's interoceptive signals however, would be less likely to adapt to changing interoceptive states and the emotions that coincide.

Drug addiction
Drug addiction is another devastating mental illness that causes significant emotional, physical and financial issues for people. Drug taking behaviour can be conceptualised as a way to avoid negative physical and mental wellbeing, and so research has found a relationship between this mental illness and interoception via insula dysfunction (Paulus & Stewart, 2014). Drug users are thought to continue using as a way to adjust their optimal level of arousal. By Schachter and Singer's Two-Factor Theory of Emotion, opioid users for example, would consume the drug, experience interoceptive processes such as slowed heart rate and breathing (Victoria Department of Health & Human Services, n.d.) (arousal), become aware of this optimal level of arousal, and then label this emotion as pleasure. A dysfunctional insular cortex would help to explain why drug users continue to seek a certain level of arousal to experience pleasure, and further perpetuate their addiction. With a hypo/hyperactivation of the insula (depending on the drug), comes atypical interoceptive processes that tell the user to continue taking drugs despite negative side effects, as a way to maintain optimal arousal and emotions (Paulus & Stewart, 2014).

Conclusion
Interoception is an important process in the human body that helps regulate physiology and emotions in order to maintain homeostasis. Relatively new and exciting research however, has discovered how the ability to accurately be aware of physiological changes in our body is actually related to improved mental health. Theories of emotion help to explain how physiological process may be involved in how emotions come to be, as emotions often coincide with physical reactions. The inability to accurately (or over accurately) be aware of your bodily processes is known as interoceptive dysfunction. As a result of a dysfunctional insular cortex, interoceptive dysfunction can exacerbate or stem from mental health issues due to the its association with emotional dysregulation. Thus, interoceptive and emotional dysregulation can lead to mental illnesses such as MDD, anorexia nervosa, PTSD, and drug addiction.

Because accurately being aware of bodily processes is so clearly linked to mental illness, this newly researched area of psychiatry is extremely important. It is vital for the research to continue to understand how to treat and prevent mental illnesses, in order to improve mental health.