Where do the interoceptive messages come from?
Interoception receives sensory information from the organs, primarily via nerve called the vagus nerve. This includes information from the stomach, lungs, kidneys, bladder, heart and intestines. The information may let the brain know that the organ is full (e.g. stomach when you have eaten too much). It also lets the brain know how the organ is working (e.g. if the heart is beating quickly or slowly). Or, as mentioned above if there is pain.
This sense also processes hormones and neurotransmitters. These are little chemicals which move around the body via the blood and other fluids in the body (e.g. the special fluid which surrounds our brain). They have a big impact on our levels of alertness and how our body functions.
There are also interoceptive receptors in the skin which give additional information. If you want to understand more about how the these messages arrive at the brain, this Wikipedia post explains it well.
Interoception – why it’s important to understand our internal state
Historically, we have focussed a lot of attention on the senses that process external information and movement. However, these only tell the brain the part of the story. The internal messages from our body provide another, very important, piece of the puzzle.
Interoception is the foundation from where we can process all of our other senses. It is the sense that helps us to regulate our body’s needs. If we are tired, it is much harder to focus. When we are really stressed, our ability to make decisions can be impaired.
If, like Tim, we don’t notice these changes in state or arousal, then we don’t make appropriate changes. Understanding our internal state is what helps us to make changes. Interoception is the key to understanding those internal sensations.