Overview
This lecture covers interoception, the body's awareness of its internal state, its underlying mechanisms, and practical ways to enhance mental and physical health by understanding and influencing brain-body communication.
What is Interoception?
- Interoception is the sensing of internal bodily states such as heartbeat, breathing, and gut sensations.
- It is central to our sense of self, influencing mood, focus, stress, sleep, and healing.
Brain-Body Communication: The Vagus Nerve
- The brain and body communicate bidirectionally, mainly via the vagus nerve (the 10th cranial nerve).
- The vagus nerve connects the brainstem to major organs, regulating functions like heart rate, breathing, digestion, and immune response.
- Sensory information sent to the brain includes mechanical (e.g., stretch, pressure) and chemical (e.g., nutrients, acidity) signals, except from the brain itself, which lacks sensory receptors.
Mechanical and Chemical Sensing in the Body
- Lungs: Inhalation increases heart rate; exhalation slows it via diaphragm and vagus nerve interactions.
- Emphasizing exhales (using a physiological sigh: double inhale, long exhale) can rapidly calm the mind.
- Emphasizing inhales or quick exhales can increase alertness and adrenaline release.
The Gut-Brain Axis
- The gut communicates fullness or emptiness to the brain through pressure and nutrient sensors.
- GLP1R neurons sense gut stretch and nutrients, signaling the brain to regulate hunger and eating behavior.
- Nutrient-sensing neurons fire based on amino acids, fatty acids, and sugars present in the gut, independent of taste.
Gut Chemistry and Microbiome
- Gut acidity/alkalinity (pH) is vital for proper organ and brain functioning.
- A healthy gut biome (good microbiota) depends on maintaining an acidic environment.
- Regular intake of fermented foods (e.g., yogurt, kimchi) lowers inflammation and improves cognitive and immune functions, outperforming high-fiber diets for reducing inflammatory markers.
Sensing Sickness: Vomiting and Fever
- The area postrema in the brainstem detects harmful blood chemicals, triggering vomiting to protect the body.
- Ginger (1–3 grams) and cannabis (THC/CBD) can help reduce nausea by acting on these neurons.
- Fever arises when neurons sense toxins in blood or cerebrospinal fluid, signaling the hypothalamus to raise body temperature and fight infection.
- To safely lower high fever, cool the palms, soles, and face, not the neck or torso, to avoid overheating the brain.
Emotions and Social Interoception
- The vagus nerve aggregates bodily signals (heart, gut, lungs) to influence emotions and facial expressions.
- Stress disrupts gut-brain communication, leading to poor digestion and mood.
- Human internal states (heart and breath) can unconsciously synchronize with others' states.
Enhancing Interoceptive Awareness
- Focusing attention on internal sensations like heartbeat strengthens brain-body connections and interoceptive awareness.
- Periodic inward focus (e.g., brief meditation or self-check-ins) can improve intuition about personal and others' feelings.
Key Terms & Definitions
- Interoception — sensing internal body signals like heartbeat, breath, and gut status.
- Vagus Nerve — main nerve for brain-body communication, affecting organs and emotions.
- GLP1R Neurons — gut neurons that sense stretch/nutrients and signal the brain about food intake.
- Microbiota — beneficial or harmful microorganisms in the gut impacting health.
- Area Postrema — brain region detecting blood-borne toxins and triggering vomiting.
- Fever — brain-triggered rise in body temperature in response to infection.
Action Items / Next Steps
- Practice focusing attention on internal sensations (e.g., heartbeat, gut fullness) for 1–2 minutes daily.
- Incorporate fermented foods into your regular diet to support gut and brain health.
- Use physiological sighs (double inhale, long exhale) to rapidly reduce stress or calm yourself.
- If experiencing high fever, cool palms, soles, and face rather than the neck or torso.