Frustrative nonreward engages midfrontal theta power and modulates effort expenditure.

Irritability is characterized by a propensity to experience frustration and has been associated with reduced self-reported willingness to expend effort for rewards. Frustration may be relevant to effortful reward pursuit, but its effects on effort expenditure have rarely been experimentally tested in humans. To address this gap, this study introduced a frustration induction in the Effort-Doors task to elicit frustrative nonreward (FNR), a negative emotional state triggered by unexpected reward loss, and examined its effects on physical effort expenditure and feedback-related electroencephalographic (EEG) activity. We also tested whether these effects vary as a function of state and trait measures of motivation and affect. Linear mixed-effects models tested the effects of FNR induction on self-reported, behavioral, and EEG measures in young adults (N = 83) completing the Frustrative Effort-Doors task. Models tested manipulation effects, trial-level post-feedback adjustment, and moderation by state and trait measures. Midfrontal theta power (MFθ) extracted using multivariate spatial filtering was examined as a function of feedback (win vs. FNR), effort (low vs. high), and subsequent behavioral adjustments. The frustration condition was associated with decreased self-reported state motivation and increased frustration, arousal, and response speed. Midfrontal theta power was larger following FNR feedback and increased with state frustration during high-effort trials. Higher state frustration was associated with reduced response vigor during effort execution following FNR feedback. MFθ did not predict trial-to-trial behavioral adjustments. These findings indicate that FNR recruits MFθ, a neural marker of cognitive control, while state frustration modulates physical effort execution following unexpected reward loss.