We are often more aware of the external physical world all around us than we are of the interior physical world of our own bodies. And yet our awareness of the body and what it feels is a key element of our physical, emotional, and mental experiences of the world. This awareness is based on a processed called interoception.
In a 2003 article reviewing research on interoception, A. Craig described what he referred to as “a distinct cortical image of homeostatic afferent activity.” As an internalized representation of how the body feels, this image:
reflects all aspects of the physiological condition of all tissues of the body… [and] engenders distinct highly resolved feelings from the body that include pain, temperature, itch, sensual touch, muscular and visceral sensations, vasomotor activity, hunger, thirst, and ‘air hunger’.
This internalized representation of the body is unique to primates. While non-primates exhibit “emotional behavior” similar to primates, their brains do not have the type of connections necessary for them to actually feel or be emotionally aware the same way we are:
The emotional behavior of non-primate mammals suggests… that they experience feelings from the body in the same way that humans do. However, the neuroanatomical evidence indicates that they cannot, because the phylogenetically new pathway that conveys homeostatic afferent activity directly to thalamocortical levels in primates is either rudimentary or absent in non-primates.
Interoception enables primates to generate an internal representation of the body and its state. However, only human beings use this representation of physical awareness to also produce a higher order representation for emotional awareness:
A re-representation of interoceptive cortical activity… is associated with subjective feelings… [I]t seems to provide an image of the physical self as a feeling (sentient) entity, which is a characteristic of human consciousness. The conclusion that the subjective image of the ‘material me’ is formed on the basis of the sense of the homeostatic condition of each individual’s body is consistent with… recent imaging studies that correlate homeostatic processing with emotional awareness.
Interoception: The sense of the physiological condition of the body | A. D. (Bud) Craig
Interoception [Image] | Ian Kleckner
How do you feel – now? The anterior insula and human awareness | A. D. (Bud) Craig