Emotional conflict affects microsaccade dynamics in the emotional face–word Stroop task

Achieving optimal performance requires effectively resolving emotional conflict arising from the interference of task-irrelevant, emotionally salient stimuli. While microsaccade behavior has been linked to various cognitive and emotional processes, whether emotional conflict affects microsaccade responses remains to be determined. Additionally, pupil dilation is known to be modulated by emotional conflict signals, and both microsaccades and pupil dilation are arguably mediated by the superior colliculus (SC). However, the relationship between microsaccades and pupil dilation remains poorly understood. In this study, we investigated the effects of emotional conflict on microsaccade rates and metrics by presenting an emotional face-word stimulus in the face-word Stroop task. Larger microsaccade amplitudes (or higher peak velocities) were observed in the incongruent condition compared to the congruent condition, while microsaccade rates were similar between the two conditions. Additionally, microsaccade amplitudes were larger in incongruent trials following congruent trials than in those following incongruent trials. Furthermore, interindividual correlations between differences in microsaccade responses and State-Trait Anxiety Inventory scores were observed. Finally, trials with lower microsaccade rates were associated with larger pupil dilation. These results demonstrate the modulation of microsaccade metrics by emotional conflict, implicating the SC in integrating signals from the locus coeruleus network to coordinate these responses.