The posterior cerebellum and inconsistent trait implications when learning the sequence of actions

Mentalizing About Dynamic Social Action Sequences Is Supported by the Cerebellum, Basal Ganglia, and Neocortex: A Meta-Analysis of Activation and Connectivity

The posterior cerebellum and anterior basal ganglia are critical subcortical structures for learning and identifying dynamic action sequences, in concert with the neocortex. The present analysis investigates the role of action sequences during social mentalizing, termed here dynamic or sequential social mentalizing. Although the role of the cerebellum in dynamic social mentalizing was extensively investigated during the last decade, the basal ganglia were long ignored. We conducted an activation likelihood estimation coordinate-based meta-analysis of sequential social mentalizing tasks (with 485 participants in 17 studies). These tasks required participants to make social mentalizing inferences ranging from low-level goals to high-level beliefs and traits, while either memorizing, generating or predicting temporal sequences of the social actions involved (i.e., social sequencing condition), or not (i.e., social non-sequencing control condition), or did so for nonsocial objects (i.e., nonsocial sequencing control condition). The tasks also occasionally included inconsistencies in social behavior. Results revealed that the cerebellum exhibited a preference for social, sequencing, and inconsistent information, while the basal ganglia showed a preference for sequencing and inconsistency, without a general preference for social input. Meta-analytic connectivity analysis further showed evidence of coactivation between mentalizing areas of the cerebellum, basal ganglia and cerebral neocortex. The present work underscores the role of subcortical structures in social mentalizing about dynamic action sequences.

Mind your step: social cerebellum in interactive navigation

The posterior cerebellum contributes to dynamic social cognition by building representations and predictions about sequences in which social interactions typically take place. However, the extent to which violations of prior social expectations during human interaction activate the cerebellum remains largely unknown. The present study examined inconsistent actions, which violate the expectations of desired goal outcomes, by using a social navigation paradigm in which a protagonist presented a gift to another agent that was liked or not. As an analogous non-social control condition, a pen was transported via an assembly line and filled with ink that matched the pen's cap or not. Participants (n = 25) were required to memorize and subsequently reproduce the sequence of the protagonist's or pen's trajectory. As hypothesized, expectation violations in social (vs non-social) sequencing were associated with activation in the posterior cerebellum (Crus 1/2) and other cortical mentalizing regions. In contrast, non-social (vs social) sequencing recruited cerebellar lobules IV-V, the action observation network and the navigation-related parahippocampal gyrus. There was little effect in comparison with a social non-sequencing control condition, where participants only had to observe the trajectory. The findings provide further evidence of cerebellar involvement in signaling inconsistencies in social outcomes of goal-directed navigation.

To Do or Not to Do: The cerebellum and neocortex contribute to predicting sequences of social intentions

Humans read the minds of others to predict their actions and efficiently navigate social environments, a capacity called mentalizing. Accumulating evidence suggests that the cerebellum, especially Crus 1 and 2, and lobule IX are involved in identifying the sequence of others' actions. In the current study, we investigated the neural correlates that underly predicting others' intentions and how this plays out in the sequence of their actions. We developed a novel intention prediction task, which required participants to put protagonists' behaviors in the correct chronological order based on the protagonists' honest or deceitful intentions (i.e., inducing true or false beliefs in others). We found robust activation of cerebellar lobule IX and key mentalizing areas in the neocortex when participants ordered protagonists' intentional behaviors compared with not ordering behaviors or to ordering object scenarios. Unlike a previous task that involved prediction based on personality traits that recruited cerebellar Crus 1 and 2, and lobule IX (Haihambo et al., 2021), the present task recruited only the cerebellar lobule IX. These results suggest that cerebellar lobule IX may be generally involved in social action sequence prediction, and that different areas of the cerebellum are specialized for distinct mentalizing functions.

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

Recent research has indicated that the posterior cerebellum plays a crucial role in social cognition by encoding sequences of social actions. This study investigates its role in learning sequences of stereotype-implying actions by group members. We presented a set of five sentences that each described a group member who performed either stereotype-consistent or inconsistent actions. Participants were instructed to memorize the temporal order of the sentences and infer a common stereotype of the group. As a comparison, we included control conditions where participants had to memorize sequences of nonsocial consistent events or simply read stereotype-consistent sentences without memorizing their order. The results showed that the posterior cerebellum was strongly activated when participants were memorizing the order of the social actions, as opposed to simply reading these social actions. More importantly, when the social actions were inconsistent as opposed to consistent with the stereotype of the group, the posterior cerebellum was activated more strongly. This activation occurred together with cortical recruitment of the mentalizing network involving the dorsomedial prefrontal cortex (dmPFC) during social actions, and additionally the conflict monitoring network involving the lateral prefrontal cortex (PFC) and posterior medial frontal cortex (pmFC) during stereotype-inconsistent actions. These findings suggest that the cerebellum supports not only learning of low-level action sequences, but also of their high-level social implications.

The posterior cerebellum and social action sequences in a cooperative context

Recent research has suggested that the posterior cerebellum encodes predictions and sequences of social actions, and also supports detecting inconsistent trait-implying actions of individuals as discussed by Pu et al. (2020, 2021). However, little is known about the role of the posterior cerebellum in detecting sequencing and inconsistencies by a group of individuals during social interaction. Therefore, the present study investigates these cerebellar functions during inconsistent trait-implying actions in a cooperative context. We presented scenarios in which two fictitious protagonists work together to accomplish a common (positive or negative) goal, followed by six sentences describing actions that implied a personality trait of the protagonists. Participants had to memorize the sequence of these actions. Crucially, the implied trait of the actions of the first protagonist contributed to achieving the goal, whereas the implied trait of the second protagonist was either consistent or inconsistent with that goal. As comparison, we added control conditions where participants had to memorize sequences of nonsocial events (implying the same characteristic of two objects), or simply read the social actions without memorizing their order. We found that the posterior cerebellum was activated while memorizing the sequence of social actions compared to simply reading these actions. More importantly, the cerebellar Crus was more strongly activated when detecting inconsistent (as opposed to consistent) actions, especially when inconsistent negative actions impeded a positive goal, relative to consistent negative actions that supported a negative goal. In conclusion, these findings confirm the crucial role of the posterior cerebellum in memorizing social action sequences and extend the cerebellar function in identifying inconsistencies in an individual's actions in a social collaborative context.

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

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.

Evidence of the role of the cerebellum in cognitive theory of mind using voxel-based lesion mapping

Theory of Mind (ToM) is a social-cognitive skill that allows the understanding of the intentions, beliefs, and desires of others. There is a distinction between affective and cognitive ToM, with evidence showing that these processes rely on partially distinct neural networks. The role of the cerebellum in social cognition has only been rarely explored. In this study, we tested whether the cerebellum is necessary for cognitive and affective ToM performance. We investigated adults with traumatic brain injury (n = 193) and healthy controls (n = 52) using voxel-based lesion-symptom mapping (VLSM) and by measuring the impact on functional connectivity. First, we observed that damage to the cerebellum affected pure Cognitive ToM processing. Further, we found a lateralization effect for the role of the cerebellum in cognitive ToM with participants with left cerebellar injury performing worse than those with right cerebellar injury. Both VLSM and standard statistical analysis provided evidence that left cerebellar Crus I and lobule VI contributed to ToM processing. Lastly, we found that disconnection of the left thalamic projection and the left fronto-striatal fasciculus was associated with poor cognitive ToM performance. Our study is the first to reveal direct causal neuropsychological evidence for a role of the cerebellum in some but not all types of ToM, processing. It reinforces the idea that social cognition relies on a complex network functionally connected through white matter pathways that include the cerebellum. It supports evidence that the neural networks underpinning the different types of ToM can be differentiated.

The Involvement of the Posterior Cerebellum in Reconstructing and Predicting Social Action Sequences

Recent advances in social neuroscience have highlighted the critical role of the cerebellum and especially the posterior cerebellar Crus in social mentalizing (i.e., theory of mind). Research in the past 5 years has provided growing evidence supporting the view that the posterior cerebellum builds internal action models of our social interactions to predict how other people's actions will be executed, and what our most likely responses to these actions will be. This paper presents an overview of a series of fMRI experiments on novel tasks involving a combination of (a) the learning or generation of chronological sequences of social actions either in an explicit or implicit manner, which (b) require social mentalizing on another person's mental state such as goals, beliefs, and implied traits. Together, the results strongly confirm the central role of the posterior cerebellar Crus in identifying and automatizing action sequencing during social mentalizing, and in predicting future action sequences based on social mentalizing inferences about others. This research program has important implications: It provides for the first time (a) fruitful starting points for diagnosing and investigating social sequencing dysfunctions in a variety of mental disorders which have also been related to cerebellar dysfunctions, (b) provides the necessary tools for testing whether non-invasive neurostimulation targeting the posterior cerebellum has a causal effect on social functioning, and (c) whether these stimulation techniques and training programs guided by novel cerebellar social sequencing insights, can be exploited to increase posterior cerebellar plasticity in order to alleviate social impairments in mental disorders.