Effective Cerebello-Cerebral Connectivity During Implicit and Explicit Social Belief Sequence Learning Using Dynamic Causal Modelling.

To study social sequence learning, earlier fMRI studies investigated the neural correlates of a novel Belief Serial Reaction Time task in which participants learned sequences of beliefs held by protagonists. The results demonstrated the involvement of the mentalizing network in the posterior cerebellum and cerebral areas (e.g., temporo-parietal junction, precuneus, temporal pole) during implicit and explicit social sequence learning. However, little is known about the neural functional interaction between these areas during this task. Dynamic causal modelling (DCM) analyses for both implicit and explicit belief sequence learning revealed that the posterior cerebellar Crus I & II were effectively connected to cerebral mentalizing areas, especially the bilateral TPJ, via closed loops (i.e., bidirectional functional connections that initiate and terminate at the same cerebellar and cerebral areas). There were more closed loops during implicit than explicit learning, which may indicate that the posterior cerebellum may be more involved in implicitly learning sequential social information. Our analysis supports the general view that the posterior cerebellum receives incoming signals from critical mentalizing areas in the cerebrum to identify sequences of social actions, and then sends signals back to the same cortical mentalizing areas to better prepare for others' social actions and one's responses to it.