Continuous theta burst stimulation to the medial posterior cerebellum impairs reversal learning in healthy volunteers.

The role of the cerebellum in associative learning and context-updating implies involvement in learning reward-punishment contingencies. This study examined the direct contribution of the cerebellum to reward- and punishment-based reversal learning. A total of 111 healthy right-handed adult volunteers received continuous theta burst stimulation (cTBS) to either the medial posterior cerebellum (n = 37), right posterolateral cerebellum (n = 37), or right occipital lobe (n = 37) in this single-blind between-subjects study. A gambling task with two changing reward-punishment contingencies (reversals) was administered to assess reversal learning rate and the implementation of the optimal strategy as primary endpoints. As secondary endpoints, heart rate variability (HRV), state anxiety, state anger, trait aggression, and trait impulsivity were assessed to examine interactions with cerebellar cTBS on the implementation of the optimal strategy. Results showed that medial posterior cerebellar cTBS compared with right posterolateral cerebellar and right occipital lobe cTBS reduced learning rate after the first reversal and diminished the implementation of the optimal strategy after learning the second reversal. No interactions of cTBS with HRV, state anxiety, state anger, trait aggression, and trait impulsivity on the implementation of the optimal strategy were observed. Our findings provide evidence for involvement of the cerebellum in reward- and punishment-based reversal learning and behavioral adaptation.