biolpsy_11

Lecture Overview

• Title: Biological Psychology 1 Lecture 11: Sensory Systems IV

• Lecturer: Dr. Richárd Reichardt

• Email: reichardt.richard@ppk.elte.hu

Interoception

• Definition:

  • The ability of the nervous system to represent the body itself.

  • Distinct from exteroception (external stimuli) and proprioception (body position).

• Components:

  • Involves the sensation of homeostatic signals.

  • Includes sensations related to heart, lung, and gastrointestinal function.

  • Itch and pain may also be considered part of interoception.

Tests of Interoception

• Key Tasks:

  • Heartbeat detection: the most common interoceptive task, easily assessed objectively.

  • Water Load Test: measures the amount of water ingested until feeling sated and completely full.

• Observation:

  • Significant individual variability in performance across different interoceptive tests.

Interoceptive Performance

• Description:

  • Refers to the accuracy of detecting objective interoceptive signals (e.g., heartbeat).

• Conscious Processing:

  • Signals are not typically processed at a conscious level.

Interoceptive Awareness

• Objective vs. Subjective:

  • Studies show a distinction between interoceptive performance (objective) and interoceptive sensitivity (subjective).

  • Participants may not be aware of their performance level on interoceptive tasks.

• Interoceptive Awareness:

  • Describes the relationship between objective performance and subjective awareness.

Interoceptive Receptors

• Historical Context:

  • Sir Charles Scott Sherrington introduced this concept; emphasized the chemical nature of interoceptive receptor activation.

• Current Understanding:

  • Interoception relies on various receptor types: chemoreceptors, thermoreceptors, mechanoreceptors.

Major Receptors in the Interoceptive System

• Carotid Body:

  • Contains glomus cells (chemoreceptors) activated by low oxygen and high CO2 concentrations.

  • Plays a critical role in cardiovascular and respiratory reflexes.

• Neuropod Cells:

  • Located in the small intestine, capable of sensing chemicals produced by the gut microbiome.

• Mechanoreception:

  • Aorta and carotid arteries house stretch-sensitive receptors with PIEZO1 and PIEZO2 ion channels, similar to somatosensory receptors.

Afferent Pathways of the Interoceptive System

• Signal Transmission:

  • Interoceptive signals travel via the vagus nerve (and cranial nerves V, VII, IX) and spinal nerves.

• Hypothesis:

  • Vagal afferents mainly carry mechanoreceptor and chemosensory signals; spinal afferents carry signals related to temperature, pain, and tissue injury.

Central Processing of Interoceptive Signals

• Nucleus of the Solitary Tract (NTS):

  • Receives information from the vagus nerve and other cranial nerves.

  • Interconnections with brainstem nuclei play a significant role.

• Insula Functionality:

  • Several studies highlight the insula's crucial role in interoceptive feelings; attention to heartbeats increases activity in posterior insular cortex (PIC).

Interoceptive Representations

• Viscerotopy:

  • NTS and insular cortex are organized like other sensory regions, exhibiting viscerotopy.

• Significance:

  • Interoception resembles the sense of smell; combinations of activated receptors may indicate distinct bodily states.

Interoception and Emotions

• Central Aspect:

  • Interoceptive feelings are crucial for emotional experiences.

• Correlation:

  • Interoceptive accuracy relates to emotional regulation and the ability to articulate emotional states.

Interoception and Mental Health

• Research Links:

  • Depression: associated with decreased interoceptive accuracy.

  • Anxiety Disorders: linked with increased interoceptive accuracy.

  • Autism Spectrum Disorder (ASD): characterized by low accuracy and awareness.

Interoception and Sickness Behavior

• Involvement with Immune System:

  • Interoception pertains to signals from the immune system; influences sickness behavior (e.g., irritability, asociality).

Conclusion

• Next Class:

  • Topic: The Motor System

• Thank You for Attention!