Midfrontal theta power relates to response speeding following frustrative nonreward

Objectives: Irritability is a transdiagnostic symptom proposed to be characterized by heightened negative affect (i.e., frustration) and maladaptive responses to frustrative nonreward (FNR). Although FNR typically elicits adaptive behavioral adjustments, the neural mechanisms that support these adjustments and their trial-by-trial dynamics remain unexplored. Midfrontal theta power, a key marker of expectancy violation and cognitive control, is a strong candidate for indexing these mechanisms and their role in supporting adaptive responses. We investigated how fluctuations in midfrontal theta power following FNR relate to subsequent behavioral adjustments and whether these associations are moderated by individual differences in irritability and state frustration. Methods: Young adults completed a validated frustration paradigm and self-reported their irritability and state frustration. A multivariate approach was used to enhance the signal-to-noise ratio of single-trial theta activity. Linear mixed-effects models tested whether trial-by-trial theta power and feedback type (win vs. FNR) predicted reaction time on the following trial. Results: Higher theta power following FNR, but not win feedback, was associated with faster reaction times on the next trial, suggesting that theta oscillations support adaptive behavioral adjustments to frustrative outcomes. Reduced theta power to FNR was linked to greater self-reported frustration, while trait irritability and state frustration did not moderate the theta-behavior association. Conclusion: Midfrontal theta power increased following FNR and predicted faster subsequent responses, highlighting its role in adaptive adjustment to unexpected reward loss. These findings enhance understanding of the neurocognitive mechanisms supporting coping with frustration and suggest this process may be less effective under heightened subjective frustration.