When fullness fails to quiet the brain: a reward-feedback signature of food addiction

Food addiction sits at an uneasy border between eating disorders and substance-use models, and one of the open mechanistic questions is whether its reward abnormalities are anticipatory (wanting before food) or consummatory (learning from the outcome). This study from the Institute of Psychology, Chinese Academy of Sciences separates the two by recording event-related potentials while participants completed a reward task in two metabolic states — hungry and satiated — using both food and monetary rewards as a within-subject control.

The anticipation phase, indexed by the stimulus-preceding negativity, told the more striking story. In healthy controls, satiety did what it physiologically should: it dampened the brain's preparatory pull toward food cues. In the food-addiction group it did not. Their SPN to food rewards was enlarged under satiety, meaning the motivational system remained primed to pursue food even when caloric need had been met. This is a neural correlate of the clinical hallmark of the condition — eating that continues past fullness, decoupled from homeostatic signals.

The feedback phase added a second, complementary deficit. The feedback-related negativity — a frontocentral signal that scales with how the brain evaluates whether an outcome was better or worse than expected — was attenuated in the food-addiction group regardless of metabolic state. Where anticipation was state-dependent (worse under satiety), feedback evaluation was state-independent, suggesting two dissociable malfunctions rather than one.

Crucially, the monetary condition showed no group differences at any phase. That control is what elevates the finding from a generic reward-deficiency claim to a food-specific one: the addicted brain is not globally hypo- or hyper-responsive to reward, it is selectively miscalibrated toward food.

Why the satiety manipulation matters

Most reward studies test a single state and average over it. By contrasting hunger and satiety the authors expose a dynamic the design would otherwise hide: the anticipatory abnormality only emerges once homeostatic satiety should have switched the appetite system off. The pathology, in other words, is less about appetite when hungry and more about the failure to release the brake when full.

Clinical reading

The blunted FRN, correlating with addiction severity and stable across states, is the more plausible trait-marker candidate; the inflated satiated SPN looks more like a state-triggered vulnerability. For clinicians, the dissociation argues against treating food addiction as simple over-wanting. Interventions that sharpen outcome learning (so that the brain registers when eating stops being rewarding) may target a different mechanism than those that merely suppress cue reactivity.