Interoception and Anorexia Nervosa Flashcards
• Links between AN and interoception • Potential variation due to modality and context and how this links to known functions of the insula • How changes in interoception might explain broader AN symptomology
what is a mechanism underlying anorexia nervosa?
interoception
anorexia nervosa
low body weight, restriction
bulimia nervosa
binge episodes, compensatory action (i.e. purging)
Binge Eating Disorder
binge episodes, no compensatory actions
there is a intuitive link between eating disorders and interoception, usually towards what system?
gastrointestinal system
what is the intuitive link between eating disorders and interoception?
failure to detect hunger - restriction (not hungry, don’t eat)
failure to detect fullness - binge eating (not satisfied, continue to eat or emotional eating)
what is some key symptomolgy of eating disorders and interoception?
- Confuse body sensations with emotions
- Difficult differentiating between emotions
- Emotion Regulation
- Alexithymia (inability to recognise and label our emotions)
what is anorexia nervosa?
- Extreme overvaluation of shape and weight
- Disturbed eating, resulting in clinically significant impairments in health and psychosocial function due to self-starvation (BMI < 18.5)
- Resistance to treatment, poor prognosis, high mortality -> psychological consequences associated with AN and physical issues through starvation
DSM-5 Criteria for Anorexia Nervosa:
- Restriction of energy intake to be less than what the body needs - leading to a significantly low body weight relative to age, sex, developmental trajectory, and physical health (cannot meet homeostatsis)
- Intense fear of gaining weight or of becoming fat
- Disturbance in the way in which one’s body weight or shape is experienced, undue influence of body weight or shape on self-evaluation (self objectification), thinking that they are larger than they are, or persistent lack of recognition of the seriousness of the current low body weight
Anorexia Nervosa presents itself as?
- Reduced capacity to soothe oneself or to empathize with others (self regulate emotions)
- Emotionally inhibited (flattening of affect)
- Depression, negative self evaluation
- Alexithymia - inability describe or recognise emotions
What is the historical link between interoception and AN?
- intuitive link between interoception and AN (hunger)
- Historical Association: ‘a failure of recognising bodily states as a characteristic’ (Bruch, 1962)
- part of Long Standing Measures (Eating Disorder Inventory) -> has an introspective deficit scale, a core aspect of diagnostic procedure people use to clinically diagnose
Eating Disorder Inventory -> Interoceptive Deficits sub scale (interoceptive sensibility). What does it look at?
A lack of confidence in recognising and accurately identifying emotions and sensations of hunger or satiety
* confusion and mistrust related to affective and bodily functioning are characteristic of eating disorders
- “I get confused about what emotion I am feeling”
- “I feel bloated after eating a normal meal”
Interoception and AN (in terms of research)
- research does not dissociate between different types of interoception that may be impacted
what two measures were not correlated in patients with AN?
sensibility and accuracy
what impacts the interpretation of visceral signals?
dysfunctional thoughts and feelings
[Jenkinson et al., 2018] Interoceptive Sensibility meta-analysis across all EDs
* EDI interoceptive scale
What did they find?
AN had significant lower scores -> show less awareness of their signals compared to others without the disorder
what did Jenkinson et al., 2018 find in relation to other disorders?
- Bulimia Nervosa (BN) equivalent effects to AN [similar disorders/diagnoses]
- Binge Eating Disorder (BED) had a smaller effect size [lower awareness compared to those without the disorder to a significant lower extent than AN and BN -> so we can suggest that a lot of the diagnostic measures are designed specifically for AN and BN]
- Lower interoception in those with higher alexithymia
What conclusions can be drawn from Jenkinson et al., 2018 research?
- Interoceptive sensibility transdiagnostic characteristic of Eds?
- But how it’s affected varies across diagnosis
- Heritable risk factor and/ important for maintenance -> inability to detect signals might maintain this disorder
- Target for therapeutic intervention?
Interoceptive Accuracy [Pollatos et al., 2008]
* The heartbeat perception task was performed using four intervals of 25 s, 35 s, 45 s and 100 s
* During all trials, participants were asked to silently count their own heartbeats -> without taking their own pulse
* Patients show a reduction in the ability to accurately perceive their heartbeat compared to healthy controls
What did they find?
- Patients with AN exhibit a generally reduced capacity to accurately perceive bodily signals
- Less intense emotional experiences in many everyday situations -> heartbeats when you’re excited or happy so flattening affect might be because they’re not detecting these feelings, fitting with symptoms
- Potential importance of interoception in the pathogenesis of AN
But findings are mixed. What does Eshkevari et al. 2014 suggest?
no difference between ED and controls (both at chance)
But findings are mixed. What are Kinnaird et al. 2020 suggest?
no difference between AN and HC in accuracy but confidence (metacognition) was difference (interoceptive awareness)
Lernia et al. (2018) conducted an Interoceptive Awareness Case Study AN and 4 HCs in a heartbeat counting task (introceptive accuracy)
* Confidence measure (Interoceptive Awareness - when compared to accuracy scores)
* MAIA (interoceptive sensibility)
What did they find?
- Trend towards lower interoceptive accuracy (but it wasn’t significantly different)
- Enhanced confidence of interoception (interoceptive awareness)
- Less able to regulate distress and distract from bodily signals, reduced body trust (interoceptive sensibility -> confidence different but accuracy is not statistically different)
- Almost total confidence in interoceptive accuracy (93/100)
- HC demonstrated alignment of accuracy and confidence (mean = 55/100)
- Detachment between ability to perceive the body and the awareness
Neural Indicator of Interoceptions (Lutz et al., 2019)
AN and HC
* Heartbeat counting task during EEG - HEP
* No significant difference in interoceptive accuracy
* significant differences in interoceptive neural processing
What did they find?
Disturbance of interoceptive signal processing at the level of cortical representation
* Higher amplitudes in HEP (heartbeat evoked potential) interval but not earlier or later control intervals (not in different time windows than expected) - around 400 m/s but with earlier ones 300 m/s -> HEP happens between 300 and 400 but went away at different intervals
Evidence for spinal thalamic path involvement: Affect Touch. The spinal thalamic pathway has two types of neurons that are involved in affective touch, what are these?
interoceptive neurones tend to be small diameter neurones with either AB delta and C Fibres
AB delta (myelinated - fast conducting - take signals like pain to the brain) and
C fibres (non-myelinated - relatively slow - take in touch information)
-> CT (or C Tactile) afferents follow the spinothalamic pathway, and a very specific slow type of touch (velocity 3-10cm/s) is needed to activate this pathway, and is associated to insula activity
In terms of afferent touch, what is it?
- touch specifically associated with pleasantness sensations, informs about physiological body state
- some evidence that affective touch can modulate/attenuate pain by following similar pathways (similar mechanisms to scratch and itch)
[Crucianelli et al., (2016)]
* AN patients given affective and neutral touch while looking at Images of faces with different facial expressions (smiling, rejecting, neutral)
* Asked for Judgments of pleasantness
* Wanted to differentiate between Anhedonia and something specific from bottom up pathway
What did they find?
- Pleasantness of affective touch was lower in AN (someone who’s smiling, more pleasant than someone who isn’t)
- Moderated by social context in both groups (but there was a general reduced pleasantness in the patient group (AN) -> because of the top-down regulation, not just a general defiicit but there’s more likely to be a difference in the bottom up in CT spinal neuro-anatomical pathway
- Difference more likely to be bottom-up that top-down
- CT - pathway
Evidence for Insula Involvement (Murialdo et al., 2007) -> looked at regulatory control of the heart, doesn’t just take in afferent information but also efferent information that adjusts the body, sending things to the body
* Regulatory control of heart rate variability in EDs using tilt table test
* Lie on a table that adjusts your body position from horizontal to vertical to simulate standing up (to see if you could see a different in heartrate in which you’d expect)
* Monitor changes in heart rate and blood pressure
- Patients had lower blood pressure
- Sympathetic cardiac activity did not increase in patients after lying to standing as occurs in healthy controls -> suggest their were some insula issues going on affecting regulatory mechanisms -> some top-down regulatory insula is also affected in these disorders
- Cardiac abnormalities similar in AN and BN even though only AN are emaciated (not linked to BMI) -> [found different in BN and AN, suggesting evidence about ageology of the disease] [remember we don’t know cause and effect so we cannot link this to BMI]
If AN patients exhibit differences in both heart rate detection / interpretation (interoceptive accuracy/awareness) and heart rate regulation. what is this consistent with?
insular cortex involvement
