Neural Responses to Reward-Associated Task-Irrelevant Scenes Under Different Perceptual Load: An fMRI Study

Value-driven attentional capture (VDAC) refers to automatic attentional capture by task-irrelevant stimuli previously associated with high rewards. Whether perceptual load modulates the neural responses to such distractors remains unclear. Using a two-day training–test fMRI paradigm, we examined behavioral and neural responses in 19 participants. On Day 1, participants performed border color discrimination while indoor and outdoor scenes were paired with different reward probabilities. On Day 2, participants performed face discrimination with perceptual load manipulated through target faces (low load: clear face; high load: noise-degraded faces), with previously rewarded scenes as irrelevant backgrounds. Test-phase correct-rejection accuracy was higher under low than high perceptual load. Whole-brain analyses revealed condition differences in the bilateral amygdala, middle temporal gyri, left inferior frontal and inferior occipital gyri, and right inferior temporal gyrus. The reward association × perceptual load interaction averaged across background repetition was nonsignificant in all three ROIs. However, the scene-selective cortex, left inferior frontal gyrus, and ventral striatum showed reward association × perceptual load × background repetition interactions. These findings suggest that perceptual load conditions may modulate reward-related repetition-sensitive neural responses, but do not establish a general load-dependent VDAC effect. Reward–category confounding and the absence of an independent assessment of reward-association acquisition limit interpretation in terms of VDAC. Face degradation additionally limits attribution of the findings to perceptual capacity.