Homeostasis (and feelings as homeostatic sensations)

The organizing principle of Craig’s account of interoception: the interoceptive system is the afferent complement of the efferent autonomic nervous system — the long-missing sensory limb of homeostasis, carried by the lamina-i-spinothalamocortical-pathway. See craig-2002-interoception, ad-craig.

Feelings are homeostatic sensations

Craig’s central claim: every feeling from the body (temperature, pain, itch, hunger, thirst, air hunger, muscular ache, sensual touch) has both a sensory and an inseparable affective/motivational aspect, and that affect is keyed to homeostatic need. The same cool stimulus is pleasant when you are overheated and aversive when “chilled to the bone” — because the feeling signals a homeostatic role and motivates behavioural correction (thermoregulation → survival). Affect is not decoration on sensation; it is the homeostatic signal.

Why this reframes pain and emotion

• Pain becomes “both a sensation and a motivation” — a homeostatic imbalance signal, not merely tissue-damage detection. Central pain is reinterpreted as thermoregulatory distress.
• Emotion becomes grounded in homeostasis: the cortical image of body state (insular-cortex) is the substrate of subjective feeling, connecting to James–Lange and the somatic-marker-hypothesis, and to embodied-selfhood (“the material me”).

Relation to allostasis and predictive accounts

Craig’s homeostasis is largely a reactive/regulatory frame (feelings report deviations to be corrected). Compare allostasis (Sterling & Eyer; stability through anticipatory change), which Farb et al. and predictive accounts foreground — where the body is regulated toward predicted set-points, not just current deviations. Craig 2009 itself gestures toward prediction (the AIC represents “predictions of future feelings”), a bridge between his homeostatic hierarchy and the predictive-coding reframing in interoceptive-inference.