Human cerebellum and social navigation: cerebello-cerebral connectivity using dynamic causal modelling.

Social navigation involves observing individuals navigating a socially rich environment sequentially while mentalizing their goals or preferences. The posterior cerebellum plays a central role in regulating human social behaviour and guiding social navigation. However, the extent to which cerebello-cerebral pathways mediate this role has not been sufficiently studied. Using Dynamic Causal Modelling on four novel social navigation studies (N = 107), our results showed many bidirectional connections between cerebellar Crus 2 and cortical mentalizing areas, including the temporoparietal junction, precuneus, and medial prefrontal cortex (mPFC), spanning both ipsilaterally and contralaterally. Connectivity patterns were only slightly modulated by experimental manipulations involving (i) active encoding versus passive observation of navigational sequences and (ii) social versus non-social sequences. Furthermore, when participants observed behaviours defying social expectations or norms, upward connectivity from the right Crus 2 to the ventral mPFC and downward connectivity from the precuneus to the left Crus 2 became stronger, while upward connectivity from the left Crus 2 to the ventral mPFC weakened. This study enhances our understanding of the role of the cerebellum in effective connectivity and its changes in response to social violations during social navigation.