Interoception

Interoception Lecture Notes

Introduction

The lecture focuses on interoception, the perception of sensations originating within the body. Interoception plays a crucial role in homeostasis, emotion regulation, and social behavior. Despite its importance, interoception has been relatively neglected in research until recent years.

Core Reading

The core reading materials are available on Moodle. It is advisable to read the assigned papers before seminars to enhance understanding and participation. Note that you cannot write about the paper you present; you need to choose another paper for your assignments.

Lecture Outline

The topics covered in this lecture include:

  1. Definitions of Interoception

  2. Dimensions of Interoception

  3. Methods to Study Interoception

  4. Neural Correlates of Interoception

  5. Is Skin an Interoceptive Organ?

  6. Examples of Interoception's Importance

Senses Beyond the Traditional Five

Besides the traditional five senses (sight, hearing, smell, touch, and taste), other senses include:

  • Temperature

  • Proprioception (position of limbs in space)

  • Vestibular sense

Interoception refers to sensations originating within our internal organs, such as heart rate, respiration, hunger, and thirst. Core temperature, as opposed to skin temperature, is undoubtedly interoceptive.

The Neglect of Interoception in Research

A significant disparity exists in research focus, with vision being extensively studied compared to other sensory modalities. Interoception, despite its critical role in survival and development, has been largely overlooked. Consider the implications of lacking interoceptive awareness:

  • Infancy: Without the ability to sense hunger, thirst, or body temperature, infants would struggle to communicate their needs.

  • Emotion Regulation: Interoception is theorized to be foundational for emotion regulation and social interaction, as infants learn to regulate their internal states through interactions with caregivers.

Homeostasis and Allostasis

The primary function of interoception is to maintain homeostasis, the body's tendency to maintain a stable equilibrium. Allostasis, a related concept, refers to the efficient regulation required to prepare the body for future needs. For example, feeling thirsty before actual dehydration occurs is an example of allostasis. Interoception is essential for predicting and adapting to the body's changing needs.

Why Are We Bad at Sensing Internal Sensations?

We are not always conscious of our internal sensations to avoid being overwhelmed. Many interoceptive signals remain below the threshold of conscious detection. Consciousness of these sensations typically arises during imbalances, such as sickness, emotional states, or physical exertion. Interoceptive sensations may also be overshadowed by exteroceptive cues. Furthermore, some sensations are referred; for example, heart sensations are often felt in the shoulder and left arm.

Despite not always being consciously perceived, interoceptive signals are always present. The brain can tune down these sensations to prevent overwhelm.

Definition of Interoception: Classical vs. Extended

  • Classical Definition: Interoception involves the processing and awareness of internal body signals generated by sensors (e.g., mechanoreceptors and chemosensors) within the body. These signals are transmitted via neural or humoral afferent pathways (from the body to the brain).

  • Extended Definition: Interoception encompasses all body sensations that carry homeostatic relevance or have motivational/affective value. This includes sensations carried by the skin, such as thermoception, cutaneous pain, and affective touch. This definition encompasses sensations processed in the posterior insula and conveyed by the spinal lamina one of the spinal thalamic tract.

The anatomical functional definition extends the classical definition by including sensations processed in the posterior insula and conveyed by the spinal lamina one of the spinal thalamic tract.

Dimensions of Interoception

Interoception is not a unidimensional phenomenon. Different dimensions, organized from bottom-up to top-down, include:

  1. Afferent Signaling: Processing of physiological signals coming from the body.

  2. Preconscious Impact of Afferent Signals: Influence of internal body states on cognition, behavior, and emotion processing, even without conscious awareness.

  3. Interoceptive Accuracy: Ability to correctly identify interoceptive sensations, measured with objective tasks.

  4. Interoceptive Sensibility: Subjective beliefs about interoceptive accuracy and attention.

  5. Interoceptive Awareness: Metacognitive awareness of interoceptive accuracy; how good we are at judging how good we are in interoception.

  6. Interoceptive Inference: Interpretation of internal signals and what we attribute them to.

Interoceptive Accuracy Measurement Tasks

  1. Heartbeat Counting Task: Participants count their heartbeats without taking their pulse during a specified time interval. The number of counted heartbeats is compared to the recorded heartbeats to assess accuracy.

    • Limitations: Participants may rely on prior knowledge of their heart rate, tasks are performed at rest.

  2. Heartbeat Discrimination Task: Participants listen to sequences of auditory tones that either match or do not match their heart rhythm and must identify whether the sequences are on beat or off beat.

    • Strengths: Knowledge of heart rate does not interfere with the task.

    • Limitations: Only sensitive to individuals with a decent level of interoceptive accuracy.

  3. Altering Arousal States: Inducing changes in arousal (e.g., via adrenaline infusion) and assessing the ability to track these changes.

    • Strengths: Measures interoception during a state of arousal.

    • Limitations: Invasive.

  4. Respiratory Resistance Task: Participants breathe through a device, and their ability to detect changes in breathing resistance is measured.

Interoceptive Sensibility Measurement

  1. Confidence Ratings: Assessing confidence in responses during heartbeat counting or discrimination tasks.

  2. Self-Report Questionnaires: Using questionnaires like the Multidimensional Assessment of Interoceptive Awareness (MAIA) or the Body Perception Questionnaire to assess subjective beliefs about interoceptive states.

  3. Alexithymia refers to difficulties in perceiving, differentiating, and expressing one's own emotions. It is often associated with interception. Although not strictly a part of it, researchers generally study both together to determine how they affect the emotional experience.

Meta-Cognitive Awareness

This refers to the match or mismatch between objective interoceptive accuracy and subjective beliefs about that accuracy. It can be measured through both one's objective ability and a confidence questionnaire. A research participant with good meta intraceptive awareness accurately identifies sensations, whereas one with poor awareness underestimates these sensations.

Neural Underpinnings of Cardiac Interoception

A network of brain regions is involved in processing interoceptive sensations:

  • Brainstem: Regulates bodily activity and relays information to higher-order structures.

  • Insula: Integrates interoceptive sensations with other information and brings sensations to awareness.

  • Anterior Cingulate Cortex (ACC)

  • Somatosensory Cortices.

Seminal Studies

  • A study using the heartbeat discrimination task in an fMRI scanner found that the anterior insula was more active and gray matter volume was associated with how good they are at the task.

  • A study using the intraceptive manipulation task (infusions of arousal): anterior insular and similar cortex were associated with better intraceptive accuracy.

Is Skin an Interoceptive Organ?

According to the extended definition of interoception, certain types of touch, particularly affective touch, can be considered interoceptive. CT afferents (C-tactile afferents) respond to slow, gentle touch and carry affective valence. These afferents are primarily found in hairy skin and are conveyed to the brain via the spinothalamic lamina one tract, projecting to the insula.

Examples and Studies on Interoception

Emotional Experience

  • Individuals with high interoceptive accuracy showed more physiological changes to emotional images and remembered them better (emotional reactivity).

  • Greater coupling between subjective and actual arousal in response to emotional images in those with higher interoceptive accuracy. These participants better understood how much they were aroused based on subjective opinions.

Decision Making

  • Better intuitive decision-making abilities (trusting gut feelings) in individuals with higher interoceptive accuracy.

  • Traders with higher interoceptive accuracy have higher performance and longer job survival.

Classical Conditioning Paradigm

Participants are presented subliminal images, followed by an electric shock and will have measure how likely they are to receive the schock.

  • Individuals with better interoceptive accuracy can better judge whether they receive shocks because they are triggered by their brain even if they do not have conscious access to.

Social Cognition

  • Interoceptive accuracy correlates with affective theory of mind (inferring others' emotional states) but not cognitive theory of mind.

  • Lesions in the insula impair emotional prosody, facial expression judgment, and mind-in-the-eyes task performance.
    *Cyberball task of social exclusion: those that received this affective touch felt less excluded (CT optimal touch).

Effective Touch

  • CT optimal touch: slow gentle touch applied to the body. Participants associated this touch with increased feelings of arousal and love. This gives social emotions for people to form better social connections.

Self-Awareness

  • Traditional Rubber Hand Illusion: When the pulsing was synchronous with the heartbeats, the individuals reported feeling the said pulses more. Suggesting the integration of cardiac information with visual, which is the degree of ownership.
    Individuals with better intraceptive accuracy were less likely to feel the rubber hand illusion.

  • Cardio visual rubber hand illusion: the study showed similar results with different paradigm (effacement delusion). However, those that were better at intraceptive accuracy were better at judging cardi visual synchronicity when modulating body awareness.

  • Infants Studies: Synchronous babies were less attuned to others, whereas out of sync babies were more attuned.

Conclusion

The way we perceive the world is always an integration between information that we receive from the external world and information that we're receiving from the internal world. This remains consistent throughout all aspects of our lives from infants up until our maturity in which we must integrate interoceptive signals (internal information) and extroceptive signals (external information).

References

References for mentioned papers and studies are included in the slides and should be easily locatable. Additionally, there are MCQs for practice with answers on the subsequent slides.