Interoception: Sensing Your Inner Body

Heartbeat, breathing, hunger, a full bladder: how the brain senses the state of the body from the inside, the role of the insula, and links to emotion, anxiety and wellbeing.

Most of the senses look outward. Interoception is the sense of the body's internal condition: heartbeat, breathing, stomach and bowel, bladder fullness, hunger and thirst, temperature, muscle effort, and more.

The pathways

Interoceptive signals travel via the vagus nerve and other cranial nerves to the brainstem's nucleus of the solitary tract, and via spinal pathways shared with pain and temperature. From there they climb to the thalamus and hypothalamus and on to the insula — the cortex folded deep inside the lateral fissure — and the anterior cingulate cortex. The neuroanatomist A. D. (Bud) Craig proposed that the front of the insula builds a moment-to-moment representation of "how I feel".

Keeping the body balanced

Interoception's first job is homeostasis: detecting when blood sugar falls, temperature drifts or carbon dioxide rises, and triggering corrections — some automatic, some by motivating behaviour, like eating or putting on a jumper. Many researchers now emphasise allostasis: the brain predicting the body's needs and acting before problems arise.

Feeling emotions

Ever since William James argued that emotions are perceptions of bodily changes, researchers have linked interoception with emotion. Theories such as Antonio Damasio's somatic marker hypothesis and Lisa Feldman Barrett's theory of constructed emotion give body signals a central role in building feelings.

Measuring it — and why it's tricky

A classic test asks people to count their heartbeats without touching their pulse. Some are accurate, many are not. However, heartbeat-counting tasks have been criticised because people may simply guess from knowledge of typical heart rates. Differences in interoception have been studied in anxiety and panic disorder (where bodily sensations may be misread as danger), eating disorders, depression and autism, and interoceptive training is being explored as a treatment. Much of this research is still early.