How do you feel? Interoception (Craig 2002)
The paper that redefined interoception for the modern field and supplied its anatomy. See ad-craig. Craig’s move: interoception is not the narrow “visceral sense” of Sherrington’s taxonomy but the sense of the physiological condition of the entire body — a homeostatic afferent system whose cortical image is the foundation of feeling, emotion, and self-awareness.
The core anatomy: the lamina I pathway
Small-diameter (Aδ and C) primary afferents innervate all tissues and report their physiological status (temperature, mechanical stress, metabolism, pH, immune/hormonal signals — far more than “pain and temperature”). They synapse in lamina I of the spinal/trigeminal dorsal horn, which projects to (a) sympathetic cell columns, (b) brainstem homeostatic centres (parabrachial, PAG, NTS/catecholaminergic groups), and (c) via a dedicated thalamic relay — VMpo (posterior ventromedial nucleus) — to the dorsal posterior insula. The nucleus of the solitary tract (NTS; vagal/parasympathetic + gustatory) relays via VMb to the same region. See lamina-i-spinothalamocortical-pathway.
This is the afferent complement of the efferent autonomic nervous system — the previously “missing” sensory limb of homeostasis. Its consequence is a reclassification: pain and temperature are interoceptive/homeostatic, distinct from the lemniscal (dorsal-column) system that carries exteroceptive touch and proprioception. This is the anatomical basis for treating pain/temperature as feelings-from-the-body rather than sub-modalities of touch (bearing on autonomic-specificity).
Feelings as homeostatic sensations
Every bodily feeling has both a sensory and an inseparable affective/motivational aspect keyed to homeostatic need — the same cool stimulus is pleasant when you are overheated and aversive when chilled. Affect signals the homeostatic role; motivation drives behavioural correction (thermoregulation → survival). “Labelled lines” (modality-selective lamina I neurons for cooling, warming, first/second pain, itch/histamine, muscle metaboreceptors) carry distinct feelings. See homeostasis; the thermal-grill-illusion (cold-inhibits-pain) is Craig’s demonstration that these are centrally compared thermosensory channels.
The insular hierarchy and the self
The primary interoceptive image (dorsal posterior insula) is re-represented anteriorly, and — in humans — lateralized to the right anterior insula (AIC), which Craig argues supports the subjective evaluation of one’s state (“how you feel”) and the sense of the physical self. Imaging links the right AIC + orbitofrontal cortex to subjective emotion (anger, disgust, sexual arousal, trustworthiness “gut reactions”). This grounds the James–Lange lineage and Damasio’s somatic-marker-hypothesis in specific anatomy, and makes the insula the seat of embodied-selfhood (“the material me”). See insular-cortex, anterior-cingulate-cortex.
Why it matters for the wiki
Craig 2002 is the bottom-up anatomical hierarchy that Seth (2013) both builds on (the posterior→anterior insula gradient, AIC as seat of subjective feeling) and departs from (Seth recasts the hierarchy as top-down predictive inference rather than ascending re-representation). That divergence is the substance of feedforward-vs-predictive-interoception — and Craig 2002 is now the primary source for the “feed-forward” pole.