Frontal theta synchronization facilitates the acquisition of new statistical regularities, evidenced by predictive eye movements

Frontal midline theta oscillations are key neural markers for learning, set-shifting, and adaptive behavior, signaling cognitive control and the reorganization of neural representations. The present study explored how these oscillations mediate the extraction and updating of statistical regularities. We delivered 6 Hz in-phase transcranial alternating current stimulation (tACS) or sham tACS, synchronizing the bilateral prefrontal cortex during an eye-tracking probabilistic sequence learning task designed to test cognitive flexibility and assess pre-stimulus gaze direction changes. A novel probabilistic sequence with a partially overlapping structure was introduced that allowed us to distinguish between the retention of old sequences and the acquisition of new ones. Following comparable statistical learning in both groups during the practice session, our results showed that tACS reduced the incorrect anticipations of previously learned triplets that remained high-probability in the new sequence and allowed participants to more flexibly anticipate triplets newly becoming high-probability. These results suggest a role of frontal midline theta in the flexible rewiring of the mental representations of prior probabilistic structures.