Frontal Theta Oscillations in Perceptual Decision-Making Reflect Cognitive Control and Confidence

Background: Perceptual decision-making requires transforming sensory inputs into goal-directed actions under uncertainty. Neural oscillations in the theta band (3–7 Hz), particularly within frontal regions, have been implicated in cognitive control and decision confidence. However, whether increased theta reflects greater effort during ambiguous decisions or more efficient control during clear decisions remains debated, and theta's relationship to stimulus clarity is incompletely understood. Purpose: To examine how task difficulty modulates theta activity and how theta dynamics evolve across the decision-making process using two complementary analytical approaches. Methods: Electroencephalography (EEG) data were acquired from 26 healthy adults performing a face/house categorization task with images containing three levels of phase noise: clear (0%), moderate (40%), and high (55%). Theta dynamics were assessed using event-related potential (ERP)-based analysis and single-trial analysis, both enhanced with current source density (CSD) methods. All p-values were corrected for multiple comparisons using non-parametric tests. Results: Frontal theta power was greater for clear than noisy stimuli (p < 0.001), suggesting that theta activity reflects cognitive control effectiveness and decision confidence rather than processing difficulty. ERP-based imaginary coherence showed stimulus-dependent modulation between frontal and parietal regions (p = 0.0133), whereas single-trial analysis revealed stable connectivity patterns unaffected by clarity (p > 0.05). Conclusions: Theta oscillations support perceptual decision-making through dual communication mechanisms—flexible task-evoked synchronization and stable intrinsic connectivity. These findings underscore the importance of methodological choices in EEG-based connectivity research and suggest an indirect link between frontal theta and decision confidence.