Age-related neural inefficiency: fNIRS evidence of prefrontal hyperactivation during emotional response inhibition

Older adults often exhibit reduced inhibitory control accompanied by altered recruitment of prefrontal networks. Whether the emotional context changes these age-related neural patterns during response inhibition remains unclear. In this study, 31 older adults and 19 young adults completed four blocks of a Go/No-Go paradigm while bilateral prefrontal cortex (PFC) activity was recorded using functional near-infrared spectroscopy (fNIRS). Blocks 1 and 2 comprised a neutral (non-emotional) Go/No-Go task using geometric shapes, while blocks 3 and 4 comprised an emotional Go/No-Go task using facial expressions (happy or angry as Go; neutral as No-Go). Task-evoked oxygenated (HbO) and deoxygenated hemoglobin (HbR) responses were quantified and analyzed at both the region-of-interest (ROI) and channel levels using linear mixed-effects models. Behaviorally, older adults showed markedly lower No-Go accuracy than young adults (p < 0.001), and emotional blocks further reduced the accuracy in both groups (p < 0.001). Crucially, reaction time analyses revealed a significant group × condition interaction (p < 0.001): young adults exhibited strategic slowing in the emotional condition, whereas older adults failed to modulate their response speed. Neurally, ROI analyses revealed robust main effects of group (older > young) and condition (emotional < neutral) on HbO across dorsolateral, dorsomedial, and ventromedial ROIs after false discovery rate correction, whereas group × condition interactions were not significant. Brain-behavior analyses revealed that higher prefrontal activation in older adults significantly predicted a poorer performance, supporting a neural inefficiency account. Translationally, these findings suggest that portable fNIRS measures of PFC inefficiency may serve as a scalable biomarker to identify older adults at risk for inhibitory-control failures-especially when emotion is present-and to track neural targets and treatment response in cognitive or emotion-regulation interventions.