Behavioral theta oscillations in cross-modal stimulus conflict and response conflict processing

Theta oscillations are closely associated with cognitive control. Accumulating evidence indicates their involvement in processing both cross-modal stimulus conflict and response conflict. However, the relationship between theta oscillations and the magnitude of these conflicts remains unclear. Research on behavioral oscillations, which shows that theta rhythms are linked to periodic patterns in behavioral performance, provides a novel perspective for investigating how theta oscillations are related to the magnitude of cross-modal stimulus conflict and response conflict. To address this issue, we used an audiovisual Stroop task with a 2-to-1 stimulus-response mapping and a time-resolved behavioral approach. Given previous evidence that sensory modality modulates theta oscillations during cross-modal stimulus conflict and response conflict processing, we conducted two experiments. In Experiment 1 (N = 43), participants responded to auditory stimuli while ignoring visual distractors (auditory task). In Experiment 2 (N = 40), participants responded to visual stimuli while ignoring auditory distractors (visual task). This design allowed us to investigate the relationship between theta oscillations and the magnitude of cross-modal stimulus and response conflicts in the auditory and visual tasks, respectively. The results demonstrated that the rhythmic processing of task-relevant stimuli was modulated by task-irrelevant stimuli. When the task-irrelevant stimuli were either the same as or different from the task-relevant stimuli (including both stimulus and response incongruency), response times exhibited rhythmic fluctuations in the theta band (4~7.5 Hz). In contrast, when task-irrelevant stimuli were neutral, the processing was characterized by oscillations in the alpha band (9.4~10 Hz). Furthermore, we found that the magnitude of the cross-modal response conflict fluctuated rhythmically at a theta frequency (3.8 Hz) in the auditory task, whereas the magnitude of the cross-modal stimulus conflict fluctuated rhythmically at a theta frequency (5.6 Hz) in the visual task. In summary, the present study demonstrates that cognitive control processes exhibit theta oscillations at the behavioral level, which directly modulate the magnitude of cross-modal stimulus conflict and response conflict. These findings elucidate the relationship between theta oscillations and conflict magnitude, and extend the rhythmic theory of attention to the domain of cognitive control in conflict processing.