Introduction to Interoception

Question 1

what is interoception?

Answer 1

• feelings we receive from the body
• signals from within the body (i.e. heart rate and hunger)
• homeostasis
• foundation of sense of physical self
• self-awareness
• emotion

Question 2

what is interoception distinct from?

Answer 2

five senses

Question 3

how did the definition of interoception initially start?

Answer 3

restrictive -> purely visceral Sherrington (1948) -> information concerning functional state of internal organs

Question 4

what is the definition of interoception now?

Answer 4

inclusive -> general homeostatic sensory capacity Craig (2002, 2003, 2008) -> information concerning the broader physiological state and the motivational needs of the body (i.e. pain, temperature, touch)

Question 5

what is homeostasis?

Answer 5

physiological equilibrium
* we tend to feel happy and healthy when at homeostasis

Question 6

neural anatomic pathway about physiological states of the body

Answer 6

follow a similar (parallel) pathway to the brain
* similar categories of the type of the afferent nerves
* signals that follow this pathway are classed as interoception (Craig 2002, 2003)

Question 7

what are afferent nerves?

Answer 7

ascending pathways (taking sensory information from the body up to the brain)

Question 8

what are efferent nerves?

Answer 8

take regulatory signals from the brain to the motor neurones in the body

Question 9

ascending pathways..

Answer 9

• afferent neurons = nerve fibres carrying information towards the brain
• different types of fibres carry different types of information and follow different pathways

Question 10

what do afferent nerves do?

Answer 10

carry information about the body’s physical state (interoception)

Question 11

what type of pathways do each afferent nerve follow?

Answer 11

similar ones

Question 12

what are some types of afferent nerves?

Answer 12

Small diameter A-delta and C-afferent nerves,
including Nociceptors (pain), thermoreceptors (temperature), osmoreceptors (thirst), baroreceptors (heart rate).

Question 13

what is different about C afferents?

Answer 13

they are unmyelinated nerve fibres

Question 14

what does it mean when nerve fibres are unmyelinated?

Answer 14

they have a relatively low conducting signal to the brain
-> comparatively slow

Question 15

what is myelination?

Answer 15

a layer of fat around the nerves which help with saltatory conduction
* more myelination -> faster conduction

Question 16

describe the process of myelination

Answer 16

• myelination is a layer of insulation (fatty sheath) surrounding a neurone
• increase efficiency of electrical transmission (nerve signals travel faster)

Question 17

what is an example of a myelinated nerve?

Answer 17

nociceptors (pain)

Question 18

what is an example of a non-myelinated nerve?

Answer 18

CT afferents (affective touch)

Question 19

where do nerve signals come from and where do they go?

Answer 19

signals come from everywhere and traject into the spinal cord

Question 20

how are the cells in the dorsal horn (of the spinal cord) divided?

Answer 20

physiologically distinct layers called laminae -> lamina I is the most superficial layer (marginal layer of the dorsal membrane)

Question 21

what is the process of a small-diameter afferent nerve?

Answer 21

1. projects to Lamina I of the dorsal horn of the spinal cord
2. projects contra laterally to the lateral spinothalamic tract
3. lamina I projects to brain-stem
4. thalamus, hypothalamus and amygdala
5. cortex (insula and anterior cingulate) termination

Question 22

neural anatomic pathways and maintaining homeostasis

Answer 22

• afferent projections from the dorsal horn provides tomato-autonomic reflexes crucial for maintaining homeostasis
• lamina I also receives descending (efferent) modulation for interoceptive signals (other part of reflex -> they come up and back down to help vasoconstructo dilation)

-> these are not emergency mechanisms but they provide continuous feedback

Question 23

the insular cortex is known as?

Answer 23

the interoceptive cortex -> cortical terminus of the pathway
* goes into the cortex -> in the fold between parietal and temporal lobe

Question 24

describe how scratching can inhibit the feeling of itch

Answer 24

scratching can inhibit the feeling of itch via inhibitory interneurons in the dorsal horn of the spinal cord
1. itch caused by a bite -> itch signals in spinal cord travel up to the brain
2. give it a scratch to alleviate itch -> send a pain signal through the parallel pain (noceiperector) nerve fibres
3. action potential signals activate inhibitory GABA interneurones -> (positive signal causes a negative signal = inhibitory effect which directly attenuate that’s signal from the itch one)
4. interaction of the spinal thalamic pathway between our pain nerve and itch nerve which is why scratch can inhibit itch temporarily)

Question 25

what are the issues if you constantly scratch your skin?

Answer 25

itch scratch cycle can occur
1. scratching the skin to alleviate itch
2. damage skin releasing inflammatory chemicals
3. stimulate nerve endings of itch afferents
4. feeling of itch leads to the urge to scratch (and so on)

Question 26

interoception and emotion

Answer 26

there is an intrinsic link between physiological state of body and emotion -> understanding our emotions involve interpreting internal bodily signals
* emotion can be felt in the body
* panic or excitement (heart rate)
* fear or surprise (muscle tension)

Question 27

what do studies suggest about physiological states?

Answer 27

they vary with different emotions

Question 28

what is the condition linked to interoception deficits?

Answer 28

alexithymia = no words for emotion (people inabilities to describe, understand or explain their emotions)

Question 29

what is ‘gut feeling’?

Answer 29

• interconnection between the gut and brain is deeply rooted in our language i.e. ‘hangry’
• neural network communicates with the brain about gastrointestinal homeostasis
• links to emotional motivation and decision making (Mayer, 2011)
• Bidirectional -> emotions can influence digestive system

Question 30

where did Aristole suggest the self was?

Answer 30

in the heart i.e. we feel our panic, fear, love in our chest and heartbeat

Question 31

where did Limanowski & Hecht (2011) suggest the self was?

Answer 31

head and heart

Question 32

where did Alsmith & Longo (2014) suggest the self was?

Answer 32

between the head and torso -> driven by physiological sensations perhaps

Question 33

Interoception and Behaviour

Answer 33

• emotional behaviours evolved to produce goal-directed actions that fulfil homeostatic needs of the body

i.e. how we feel can be moderated by physiological state of the body (vasoconstriction)
* how you feel can influence your behaviour (too hot -> take jumper off)

Question 34

physiological motivations

Answer 34

cognition takes place within the context of our body that needs to stay alive and be healthy

Question 35

how has the brain evolved to regulate bodies within a social context

Answer 35

can tell us about how we experience different sensory stimuli and it might change depending on our physiological state i.e. chocolate cake -> already eaten three slices, body says we’re full and therefore our emotions and behaviours are negative and we no longer want the cake

Question 36

Affective experience influenced by the current body state, how?

Answer 36

interoception drive our behaviour and emotions to achieve and maintain homeostasis (the desirable physiological state)
* too hot -> cold shower
* full -> no cake

Question 37

Garkfinkel et al., (2014)
- used an attentional blink (AB) paradigm -> temporal capacity of limits of attention (edge of our capacity of awareness)
- identification of an initital target (T1 - always a house) during a rapid serial visual presentation (RSVP) of stimuli impairs the ability to detect a second target (always a face) [this is the paradigm they used]
- stimuli in the RSVP presented in time with different phases of the cardiac cycle (when signal comes in which each heartbeat -> when the heart contracts (systole) or relaxes (diastole)
* had different condition: one stimuli was timed locked to the systole phase and one to the diastole phase
- Target 1 was always a house, T2 was a face (disgust, fear, sad, happy or neutral) and the result of the stimuli were scrambled images

• Following the initial Attention Blink task was a second task to examine recognition of T1 and T2 stimuli presented in preceding RSVP.
• Participants given three options for T1 and T2 (target and 2 distractors). -> because it’s at limits of their capacity, it’s likely they’ll struggle to remember

Answer 37

• Timing of stimuli facilitated detection of T2 for fear faces only -> systole presentation led to greater proportion of fear faces detected.
• People were much more accurate to detect faces when stimuli where timed with the interactions of the heart
  *being able to time lock a physiological state, trying to isolate the role of that physiological state

Question 38

why did they use the cardiac cycle?

Answer 38

because baroreceptors (in arterial coronary domain) from the heart convey information about the strength and timing of the heartbeat through the pathway to the brain which facilitates modulation modulation of blood pressure through vasodilation / vasoconstriction to maintain equibliruim.
* These signals also communicate to the brain and regions associated with emotion and cognition (insular, amygdala)
* because this information gets sent up to the brain -> makes sense that there might be a link between heartbeat and cognitions and emotions

• systole (contraction of the heart)
• diastole (heart is relaxed)

Question 39

Garkfinkel et al., (2014) conducted a second MRI experiment
- Neutral or Fear faces presented briefly (100ms)
- Time locked to an individual’s heartbeat
- emotion intensity rating about how intense the emotions of the face were

Answer 39

• Timing of the stimuli related to intensity judgments.
• Systole stimuli led to greater intensity for fear faces.
• Diastole stimuli trend for greater intensity for neutral faces (but this was not significant).
• Findings related to individual differences in state anxiety

Question 40

Garkfinkel et al., (2014) in terms of MRI:

Answer 40

• main effect of the stimulus timing associated with activity in the anterior insula
• interaction between cardiac timing and emotion (of faces) associated with amygdala activity

Question 41

what does Garkfinkel et al., (2014) suggest?

Answer 41

• Neural processing and conscious experience of sensory (emotion) stimuli are modulated by the visceral state.
• Detection and intensity of fear faces was facilitated by systole presentation.
• Cardiac presentation linked to anterior insular activity
• Amygdala activity sensitive to phase of cardiac cycle and predicted shifts in emotion (because amygdala is involved in emotion).
• Effects related to state levels of anxiety – altered heart-emotion coupling could be related to anxiety.

Question 42

what are some conclusions drawn from Garkfinkel et al., (2014) research?

Answer 42

• Perception of threat (fear detection/intensity) dependent on level of physiological arousal.
• In systole the heart is working hardest.
• Greater arousal (more and stronger heartbeats) would mean more time in systole compared to diastole.

Question 43

Azevedo et al. (2017) takes a similar paradigm but for more complex human behaviours -> examined the effect of cardiac cycle on racial stereotyping.
* comparing stimulus presentation when the muscle is contracting (Systole) with when it is relaxing (Diastole).

• Identify targets (tool or a weapon)
• All participants were white
• Primed by Black or White males faces
• Congrunet (weapon paired with a black face), Incongruent (weapon paired with a spanner)
• Stimuli were presented at Systole or Diastole

Answer 43

• systole exacerbated racially stereotyped responses
• more accurate at detecting tools when accompanied by a white face, while more likely to detect weapon when accompanied by a black face

Question 44

Azevedo et al. (2017) First Shooter Task found:

• sample was white

Answer 44

• participants chose to shoot unarmed black men more often than unarmed white men

Question 45

what conclusions can we draw from Azevedo et al. (2017) research?

Answer 45

• in the context of potential threatening stimuli heightened representation of cardiac signals in the brain (when the heart is working hardest) may enhance salience of social cues and promote negative racial stereotypes.
• Important brain-body mechanism influencing processing of salient social cues and subsequent actions.
• Prediction-based on previous social associations moderated by current body state.

Question 46

what is interoception?

Answer 46

internal bodily signals concerning physiological state of the body

Question 47

what do interoceptive signals modulate?

Answer 47

physiological state (interoceptive signals) modulate emotion and behaviour