The posterior cerebellum and temporoparietal junction support explicit learning of social belief sequences

Abstract

This study tests the hypothesis that the posterior cerebellum is involved in social cognition by identifying and automatizing sequences of social actions. We applied a belief serial reaction time task (Belief SRT task), which requires mentalizing about two protagonists' beliefs about how many flowers they receive. The protagonists' beliefs could either be true or false depending on their orientation (true belief: oriented towards and directly observing the flowers; or false belief: oriented away and knowing only prior information about flowers). A Control SRT task was created by replacing protagonists and their beliefs with shapes and colors. Participants were explicitly told that there was a standard sequence related to the two protagonists' belief orientations (Belief SRT task) or the shapes' colors (Control SRT task). Both tasks included a Training phase where the standard sequence was repeated and a Test phase where this standard sequence was interrupted by random sequences. As hypothesized, compared with the Control SRT task, the Belief SRT task recruited the posterior cerebellar Crus II and the temporoparietal junction (TPJ) more. Faster response times were correlated with less Crus II activation and with more TPJ activation, suggesting that the Crus II supported automatizing the belief sequence while the TPJ supported inferring the protagonists' beliefs. Also as hypothesized, compared with an implicit version of the Belief SRT task (i.e., participants did not know about the existence of sequences; Ma, Pu, et al., 2021b), the cerebellar Crus I &II was engaged less during initial training and automatic application of the sequence, and the cortical TPJ was activated more in processing random sequences.

This is not who you are: The posterior cerebellum and stereotype-inconsistent action sequences

“…In line with our hypothesis, our results confirmed that the posterior cerebellum contributes to memorizing social action sequences as opposed to simply reading and recognizing social actions that implied a consistent group stereotype. This finding extends prior research demonstrating the general role of the posterior cerebellar Crus in action sequencing along a large variety of social mentalizing tasks, most often without any a priori inherent order, including memorizing the temporal order of trait-implying actions (Pu et al, 2020(Pu et al, , 2021, predicting social action sequences based on personality traits (Haihambo et al, 2021), memorizing social trajectories involved in goal-directed navigation (Li et al, 2021), and even implicitly learning the order of others' beliefs (Ma et al, 2021b). Together, these studies confirmed the "sequence hypothesis" (Leggio & Molinari, 2015) applied to social cognition (Van Overwalle et al, 2019b), which states that the cerebellum identifies and encodes sequences of actions in the social domain.…”

A narrative sequencing and mentalizing training for adults with autism: A pilot study

“…Understanding this sequence is a process subserved by cerebellar sequencing functions–a necessary process that leads to the recognition of social signals and requires mentalizing about the intentions or beliefs behind these social cues. This idea has been corroborated by a variety of sequence-based mentalizing tasks (e.g., Pu et al, 2020 ; Haihambo et al, 2021 ; Heleven et al, 2021 ; Li et al, 2021 ; Ma et al, 2021a , b ). Several connectivity studies have uncovered bidirectional connections between the cerebellum and neocortical mentalizing areas which constitute the larger part of the default mode network ( Habas et al, 2009 ; Krienen and Buckner, 2009 ; Buckner et al, 2011 ; Van Overwalle and Mariën, 2016 ; Van Overwalle et al, 2019b , 2020 ).…”