Kris Baetens

Understanding others' actions and goals by mirror and mentalizing systems: a meta-analysis.

This meta-analysis explores the role of the mirror and mentalizing systems in the understanding of other peoples action goals. Based on over 200 fMRI studies, this analysis demonstrates that the mirror system - consisting of the anterior intraparietal sulcus and the premotor cortex - is engaged when one perceives articulated motions of body parts irrespective of their sensory (visual or auditory) or verbal format as well as when the perceiver executes them. This confirms the matching role of the mirror system in understanding biological action. Observation of whole-body motions and gaze engage the posterior superior temporal sulcus and most likely reflects an orientation response in line with the action or attention of the observed actor. In contrast, the mentalizing system - consisting of the temporo-parietal junction, the medial prefrontal cortex and the precuneus - is activated when behavior that enables inferences to be made about goals, beliefs or moral issues is presented in abstract terms (e.g., verbal stories or geometric shapes) and there is no perceivable biological motion of body parts. A striking overlap of brain activity at the temporo-parietal junction between social inferences and other, non-social observations (e.g., Posners cuing task) suggests that this area computes the orientation or direction of the behavior in order to predict its likely end-state (or goal). No conclusions are drawn about the specific functionality of the precuneus and the medial prefrontal cortex. Because the mirror and mentalizing systems are rarely concurrently active, it appears that neither system subserves the other. Rather, they are complementary. There seems, however, to be a transition from the mirror to the mentalizing system even when body-part motions are observed by perceivers who are consciously deliberating about the goals of others and their behavioral executions, such as when perceived body motions are contextually inconsistent, implausible or pretended.

Social cognition and the cerebellum: a meta-analysis of over 350 fMRI studies.

This meta-analysis explores the role of the cerebellum in social cognition. Recent meta-analyses of neuroimaging studies since 2008 demonstrate that the cerebellum is only marginally involved in social cognition and emotionality, with a few meta-analyses pointing to an involvement of at most 54% of the individual studies. In this study, novel meta-analyses of over 350 fMRI studies, dividing up the domain of social cognition in homogeneous subdomains, confirmed this low involvement of the cerebellum in conditions that trigger the mirror network (e.g., when familiar movements of body parts are observed) and the mentalizing network (when no moving body parts or unfamiliar movements are present). There is, however, one set of mentalizing conditions that strongly involve the cerebellum in 50-100% of the individual studies. In particular, when the level of abstraction is high, such as when behaviors are described in terms of traits or permanent characteristics, in terms of groups rather than individuals, in terms of the past (episodic autobiographic memory) or the future rather than the present, or in terms of hypothetical events that may happen. An activation likelihood estimation (ALE) meta-analysis conducted in this study reveals that the cerebellum is critically implicated in social cognition and that the areas of the cerebellum which are consistently involved in social cognitive processes show extensive overlap with the areas involved in sensorimotor (during mirror and self-judgments tasks) as well as in executive functioning (across all tasks). We discuss the role of the cerebellum in social cognition in general and in higher abstraction mentalizing in particular. We also point out a number of methodological limitations of some available studies on the social brain that hamper the detection of cerebellar activity.

Involvement of the mentalizing network in social and non-social high construal

The dorsomedial prefrontal cortex (dmPFC) is consistently involved in tasks requiring the processing of mental states, and much rarer so by tasks that do not involve mental state inferences. We hypothesized that the dmPFC might be more generally involved in high construal of stimuli, defined as the formation of concepts or ideas by omitting non-essential features of stimuli, irrespective of their social or non-social nature. In an fMRI study, we presented pictures of a person engaged in everyday activities (social stimuli) or of objects (non-social stimuli) and induced a higher level of construal by instructing participants to generate personality traits of the person or categories to which the objects belonged. This was contrasted against a lower level task where participants had to describe these same pictures visually. As predicted, we found strong involvement of the dmPFC in high construal, with substantial overlap across social and non-social stimuli, including shared activation in the vmPFC/OFC, parahippocampal, fusiform and angular gyrus, precuneus, posterior cingulate and right cerebellum.

Traits are represented in the medial prefrontal cortex: an fMRI adaptation study

Neuroimaging studies on trait inference about the self and others have found a network of brain areas, the critical part of which appears to be medial prefrontal cortex (mPFC). We investigated whether the mPFC plays an essential role in the neural representation of a trait code. To localize the trait code, we used functional magnetic resonance imaging (fMRI) adaptation, which is a rapid suppression of neuronal responses upon repeated presentation of the same underlying stimulus, in this case, the implied trait. Participants had to infer an agents (social) trait from brief trait-implying behavioral descriptions. In each trial, the critical (target) sentence was preceded by a sentence (prime) that implied the same trait, the opposite trait, or no trait at all. The results revealed robust adaptation from prime to target in the ventral mPFC only during trait conditions, as expected. Adaptation was strongest after being primed with a similar trait, moderately strong after an opposite trait and much weaker after a trait-irrelevant prime. This adaptation pattern was found nowhere else in the brain. In line with previous research on fMRI adaptation, we interpret these findings as indicating that a trait code is represented in the ventral mPFC.

N400 and LPP in spontaneous trait inferences.

Past research on spontaneous trait inferences using event related potentials (ERPs) has consistently reported increased late positive potential (LPP) amplitudes following social expectancy violations, but no N400 modulation. In the present study, participants read scenarios describing behaviors of unknown actors. They entailed descriptions of several positive trait implying behaviors, followed by a single final sentence describing behavior that was either consistent or inconsistent with the previously implied trait. As in previous studies, we found significantly increased LPP amplitudes following inconsistent behaviors at multiple frontal sites. Unlike in previous research, we also found increased N400 amplitudes at several centro-parietal sites. The divergence of these results is explained from minor differences in the stimulus presentation procedure and possible overlap of ERP components of opposite polarity. Temporal principal component analysis (PCA) confirmed the separate influence of concurrent LPP and N400 ERP modulations, and the source of the largest factors was located using sLORETA. It is suggested that the increased N400 in response to trait inconsistencies reflects difficulties in understanding unanticipated behavior, while the LPP effect might reflect evaluative incongruence.

Cerebellar areas dedicated to social cognition? A comparison of meta-analytic and connectivity results.

A recent meta-analysis explored the role of the cerebellum in social cognition and documented that this part of the brain is critically implicated in social cognition, especially in more abstract and complex forms of mentalizing. The authors found an overlap with clusters involved in sensorimotor (during mirror and self-judgment tasks) as well as in executive processes (across all tasks) documented in earlier nonsocial cerebellar meta-analyses, and hence interpreted their results in terms of a domain-general function of the cerebellum. However, these meta-analytic results might be interpreted in a different, complementary way. Indeed, the results reveal a striking overlap with the parcellation of cerebellar topography offered by a recent functional connectivity analysis. In particular, the majority of social cognitive activity in the cerebellum can also be explained as located within the boundaries of a default/mentalizing network of the cerebellum, with the exception of the involvement of primary and integrative somatomotor networks for self-related and mirror tasks, respectively. Given the substantial overlap, a novel interpretation of the meta-analytic findings is put forward suggesting that cerebellar activity during social judgments might reflect a more domain-specific mentalizing functionality in some areas of the cerebellum than assumed before.

Dissociation of a trait and a valence representation in the mPFC

A previous functional MRI adaptation study on trait inference indicated that a trait code is located in the ventral medial prefrontal cortex (vmPFC), but could not rule out that this adaptation effect is due to the traits underlying valence. To address this issue, we presented sentences describing positive and negative valences of either a human trait or object characteristic, and manipulated whether the human trait or object characteristic was repeated or not, either with the same or opposite valance. In two trait conditions, a behavioral trait-implying sentence was preceded by a prime sentence that implied the same or the opposite trait. The results confirmed the earlier finding of robust trait adaptation from prime to target in the vmPFC, and also found adaptation in the precuneus and right mid-occipital cortex. In contrast, no valence adaptation was found in two novel object conditions, in which the target sentence again implied a positive or negative trait, but was preceded by a prime sentence that described an object with the same or the opposite valence. Together with the previous study, this indicates that a specific trait code, but not a generalized valence code, is represented in the vmPFC.

Nice or nerdy? The neural representation of social and competence traits

ABSTRACT This study investigates to what extent social and competence traits are represented in a similar or different neural trait code. To localize these trait codes, we used functional magnetic resonance imaging repetition suppression, which is a rapid reduction of neuronal responses upon repeated presentation of the same implied trait. Participants had to infer an agent’s trait from brief trait-implying behavioral descriptions. In each trial, the critical target sentence was preceded by a prime sentence that implied the same trait or a different competence-related trait which was also opposite in valence. The results revealed robust repetition suppression from prime to target in the ventral medial prefrontal cortex (mPFC) given a similar (social) as well as a dissimilar (competence) prime. The suppression given a similar prime confirms earlier research demonstrating that a trait code is represented in the ventral mPFC. The suppression given a dissimilar prime is interpreted as indicating that participants categorize a combination of competence and social information into novel subcategories, reflecting nice (but incompetent) or nerdy (but socially awkward) traits. A multi-voxel pattern analysis broadly confirmed these results, and pinpointed the inferior parietal cortex, cerebellum, temporo-parietal junction and mPFC as areas that differentiate between social and competence traits.

Social Versus Nonsocial Reasoning

Does social reasoning rely on different processes than other forms of reasoning do? Direct and meta-analytical comparisons of social and nonsocial reasoning have consistently reported stronger engagement of the mentalizing network (encompassing the medial prefrontal cortex, precuneus, and temporoparietal junction) in social reasoning, but other studies on nonsocial reasoning also implicate the mentalizing network. Recent research suggests that the mentalizing system is associated with domain-general processes related to attention reallocation and meaning retrieval. Although not only social reasoning requires these capacities, they may have evolved primarily to serve social functioning.

The Dorsal Medial Prefrontal Cortex Is Recruited by High Construal of Non-social Stimuli

The dorsomedial prefrontal cortex (dmPFC) is part of the mentalizing network, a set of brain regions consistently engaged in inferring mental states. However, its precise function in this network remains unclear. It has recently been proposed that the dmPFC is involved in high-level abstract (i.e., categorical) identification or construction of both social and non-social stimuli, referred to as “high construal.” This was based on the observation of greater activation in the dmPFC shared by a high construal social condition (trait inference based on visually presented behavior) and a high construal non-social condition (categorization of visually presented objects) vs. matched low construal conditions (visual description of the same pictures). However, dmPFC activation has been related to task contexts requiring responses based on self-guided generation of mental content or decisions as compared to responses more directly determined by the experimental context (e.g., free vs. rule-governed choice). The previously reported dmPFC activity may reflect differences in task constraint (i.e., the extent to which the task context guided the process) confounded with the construal manipulation. Therefore, in the present study, we manipulated construal level and constraint independently, while participants underwent functional magnetic resonance imaging (fMRI). As before, participants visually described (low level construal) or categorized (high level construal) pictures of objects. Orthogonal to this, the description or categorization task had to be performed on either one object (low constraint) or on two objects simultaneously (high constraint), limiting the number of possible responses. Statistical analysis revealed common greater activation in both high construal conditions (high and low constraint) than in their low construal counterparts, replicating the influence of construal level on dmPFC activation (greater involvement in high than low construal), but no influence of constraint. In line with previous proposals and earlier work, we suggest that the dmPFC is involved in high-construal abstraction across different domains.