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

Background: Perceptual decision-making under noisy conditions 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 changes in theta oscillations reflects greater effort during ambiguous decisions or more efficient control during clear conditions 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 scrambed phase and Gaussian noise: clear (0%), moderate (40%), and high (55%). Theta activity dynamics were assessed from current source density (CSD) time courses of event-related potentials (ERPs) and single-trials. Results: Frontal theta power was greater for clear than noisy stimuli (corrected 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 (corrected p = 0.0133), whereas single-trial analysis revealed stable connectivity patterns unaffected by clarity (corrected 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 a link between frontal theta and decision confidence.