Autism and psychosis as diametrical disorders of embodiment

Beyond body image: Self-face recognition and negative self-face evaluations in women at high risk for an eating disorder

BACKGROUND

Although one's face represents a core aspect of one's physical appearance, it remains underexplored in eating disorder (ED) populations.

AIMS

The current study examined whether self-face recognition accuracy and evaluations differ in those at high (vs. low) ED risk. We also explored whether recognition accuracy and evaluations are related, and whether this relationship is moderated by ED risk status.

MATERIALS & METHODS

Participants included 222 women of East/Southeast Asian (61%) and Caucasian (39%) ethnicity, stratified into low-ED-risk (n = 124) and high-ED-risk (n = 98). Participants completed measures of self-face recognition accuracy (difficulty recognizing their face and sensitivity to seeing their facial image) and evaluations (including perceived facial adiposity and attractiveness, and head dissatisfaction).

RESULTS

Partially consistent with hypotheses, regression analyses revealed that participants at high (vs. low) risk showed poorer self-face recognition accuracy (greater difficulty) and more negative self-face evaluations (higher perceived adiposity, lower perceived attractiveness, greater head dissatisfaction). However, ED risk was not significantly associated with self-face recognition sensitivity. Inconsistent with expectations, whilst greater self-face recognition difficulty was associated with more negative self-face evaluations, ED risk failed to moderate such effects.

DISCUSSION & CONCLUSION

Findings suggest the potential value of considering face and body image disturbances in ED research and interventions. Further research is encouraged.

Identifying overlapping and distinctive traits of autism and schizophrenia using machine learning classification

INTRODUCTION

Autism spectrum disorder (ASD) and schizophrenia spectrum disorder (SSD) share some symptoms. We conducted machine learning classification to determine if common screeners used for research in non-clinical and subclinical populations, the Autism-Spectrum Quotient (AQ) and Schizotypal Personality Questionnaire - Brief Revised (SPQ-BR), could identify non-overlapping symptoms.

METHODS

1,397 undergraduates completed the SPQ-BR and AQ. Random forest classification modelled whether SPQ-BR item scores predicted AQ scores and factors, and vice versa. The models first used all item scores and then the least/most important features.

RESULTS

Robust trait overlap allows for the prediction of AQ from SPQ-BR and vice versa. Results showed that AQ item scores predicted 2 of 3 SPQ-BR factors (disorganised, interpersonal), and SPQ-BR item scores successfully predicted 2 of 5 AQ factors (communication, social skills). Importantly, classification model failures showed that AQ item scores could not predict the SPQ-BR cognitive-perceptual factor, and the SPQ-BR item scores could not predict 3 AQ factors (imagination, attention to detail, attention switching).

CONCLUSIONS

Overall, the SPQ-BR and AQ measure overlapping symptoms that can be isolated to some factors. Importantly, where we observe model failures, we capture distinctive factors. We provide guidance for leveraging existing screeners to avert misdiagnosis and advancing specific/selective biomarker identification.

On the varieties of conscious experiences: Altered Beliefs Under Psychedelics (ALBUS)

How is it that psychedelics so profoundly impact brain and mind? According to the model of "Relaxed Beliefs Under Psychedelics" (REBUS), 5-HT2a agonism is thought to help relax prior expectations, thus making room for new perspectives and patterns. Here, we introduce an alternative (but largely compatible) perspective, proposing that REBUS effects may primarily correspond to a particular (but potentially pivotal) regime of very high levels of 5-HT2a receptor agonism. Depending on both a variety of contextual factors and the specific neural systems being considered, we suggest opposite effects may also occur in which synchronous neural activity becomes more powerful, with accompanying "Strengthened Beliefs Under Psychedelics" (SEBUS) effects. Such SEBUS effects are consistent with the enhanced meaning-making observed in psychedelic therapy (e.g. psychological insight and the noetic quality of mystical experiences), with the imposition of prior expectations on perception (e.g. hallucinations and pareidolia), and with the delusional thinking that sometimes occurs during psychedelic experiences (e.g. apophenia, paranoia, engendering of inaccurate interpretations of events, and potentially false memories). With "Altered Beliefs Under Psychedelics" (ALBUS), we propose that the manifestation of SEBUS vs. REBUS effects may vary across the dose-response curve of 5-HT2a signaling. While we explore a diverse range of sometimes complex models, our basic idea is fundamentally simple: psychedelic experiences can be understood as kinds of waking dream states of varying degrees of lucidity, with similar underlying mechanisms. We further demonstrate the utility of ALBUS by providing neurophenomenological models of psychedelics focusing on mechanisms of conscious perceptual synthesis, dreaming, and episodic memory and mental simulation.

I tweet, therefore I am: a systematic review on social media use and disorders of the social brain

With rapid technological advances, social media has become an everyday form of human social interactions. For the first time in evolutionary history, people can now interact in virtual spaces where temporal, spatial, and embodied cues are decoupled from one another. What implications do these recent changes have for socio-cognitive phenotypes and mental disorders? We have conducted a systematic review on the relationships between social media use and mental disorders involving the social brain. The main findings indicate evidence of increased social media usage in individuals with psychotic spectrum phenotypes and especially among individuals with disorders characterized by alterations in the basic self, most notably narcissism, body dysmorphism, and eating disorders. These findings can be understood in the context of a new conceptual model, referred to here as 'Delusion Amplification by Social Media', whereby this suite of disorders and symptoms centrally involves forms of mentalistic delusions, linked with altered perception and perpetuation of distorted manifestations of the self, that are enabled and exacerbated by social media. In particular, an underdeveloped and incoherent sense of self, in conjunction with 'real life' social isolation that inhibits identify formation and facilitates virtual social interactions, may lead to use of social media to generate and maintain a more or less delusional sense of self identity. The delusions involved may be mental (as in narcissism and erotomania), or somatic (as in body dysmorphic disorder and eating disorders, encompassing either the entire body or specific body parts). In each case, the virtual nature of social media facilitates the delusionality because the self is defined and bolstered in this highly mentalistic environment, where real-life exposure of the delusion can be largely avoided. Current evidence also suggests that increased social media usage, via its disembodied and isolative nature, may be associated with psychotic spectrum phenotypes, especially delusionality, by the decoupling of inter and intra-corporeal cues integral to shared reality testing, leading to the blurring of self-other boundaries.

The Values-Based Psychopathology of Antoni Kępiński (1918-1972)

BACKGROUND

The question of the role of personal values in the constitution of and recovery from mental illness is a divisive subject discussed in contemporary psychopathology. This article critically examines the psychopathological theories and contributions of Antoni Kępiński - a seminal yet internationally under-recognized Polish psychiatrist.

SUMMARY

Drawing upon a multilayered framework incorporating biological, affective-emotional, and sociocultural dimensions, Kępiński posited mental disorders as disturbances in the energy and information metabolism with the environment leading to an increase in entropy. Kępiński's work also contributes to a richer understanding of schizophrenia (whose essence he metaphorically described as the plasma membrane rupture) and the complexities inherent in the decision-making processes of patients. In a quasi-phenomenological vein, Kępiński encouraged to re-evaluate delusions and hallucinations as opportunities to access unfiltered insights into reality. He also argued for the potential for moral growth within psychiatric treatment.

KEY MESSAGES

Kępiński's theories anticipated many concepts now foundational in neuroscientific research and clinical psychiatry, showcasing his role as a forward-thinking figure in the history of the profession.

Enfacement illusions: Filling a knowledge gap in eating disorder risk assessment, prevention, and intervention?

Body image disturbance (BID) is central to eating disorders (EDs), yet the role of self-face perception has received limited empirical attention despite rising sociocultural pressures emphasizing facial appearance through technologies such as social media. Emerging evidence suggests impairments in self-face recognition accuracy and distorted perceptions of facial appearance among individuals with EDs. Enfacement illusions, involving the experimental induction of perceived ownership over another's face, offer a novel paradigm to comprehensively investigate the perceptual multisensory integration processes underlying self-face perception disturbances in ED populations. Such an approach may hold promise for elucidating core pathological mechanisms contributing to BID and ED psychopathology. We discuss how rigorous investigation of self-face perception through the enfacement illusion paradigm represents an innovative direction of research and/or clinical application that may advance etiological models of EDs and possibly inform interventions targeting the potentially multidimensional nature of body and facial image disturbances characterizing EDs. PUBLIC SIGNIFICANCE STATEMENT: Body image disturbance is central to eating disorders (EDs), yet, the role of face-related disturbances remains critically under-investigated. After summarizing findings on face-related disturbances in EDs we propose how enfacement illusions (i.e., the experimental induction of ownership over another's face) may elucidate self-face perception disturbances in EDs, and their underlying mechanisms. Enfacement illusions may also offer an intervention to potentially address multifaceted face and body image disturbances characterizing EDs.

Agency in schizophrenia and autism: a systematic review

Introduction

Previous research suggests that altered experiences of agency are an underlying vulnerability in both schizophrenia and autism. Here, we explore agency as a potential transdiagnostic factor by conducting a systematic review of existing literature investigating agency in autism and schizophrenia individually and together.

Methods

Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, we conducted three systematic searches on PsycINFO, Embase, Medline, PubMed and Web of Science to identify studies that investigated (1) agency in schizophrenia, (2) agency in autism, and (3) agency in both schizophrenia and autism.

Results

A total of 31 articles met eligibility criteria for inclusion and data extraction, with 24 measuring agency in schizophrenia, 7 investigating agency in autism, and no articles comparing the two. Results show that, compared to control populations, agency is significantly different in every identified schizophrenia study and generally not significantly different in autism.

Discussion

Importantly, we identified a lack of studies using common tasks and a disproportionate number of studies investigating different dimensions of agency across the two conditions, resulting in limited grounds for valid comparison.

Systematic review registration

Prospero, CRD42021273373.

Evolutionary psychiatry: foundations, progress and challenges

Evolutionary biology provides a crucial foundation for medicine and behavioral science that has been missing from psychiatry. Its absence helps to explain slow progress; its advent promises major advances. Instead of offering a new kind of treatment, evolutionary psychiatry provides a scientific foundation useful for all kinds of treatment. It expands the search for causes from mechanistic explanations for disease in some individuals to evolutionary explanations for traits that make all members of a species vulnerable to disease. For instance, capacities for symptoms such as pain, cough, anxiety and low mood are universal because they are useful in certain situations. Failing to recognize the utility of anxiety and low mood is at the root of many problems in psychiatry. Determining if an emotion is normal and if it is useful requires understanding an individual's life situation. Conducting a review of social systems, parallel to the review of systems in the rest of medicine, can help achieve that understanding. Coping with substance abuse is advanced by acknowledging how substances available in modern environments hijack chemically mediated learning mechanisms. Understanding why eating spirals out of control in modern environments is aided by recognizing the motivations for caloric restriction and how it arouses famine protection mechanisms that induce binge eating. Finally, explaining the persistence of alleles that cause serious mental disorders requires evolutionary explanations of why some systems are intrinsically vulnerable to failure. The thrill of finding functions for apparent diseases is evolutionary psychiatry's greatest strength and weakness. Recognizing bad feelings as evolved adaptations corrects psychiatry's pervasive mistake of viewing all symptoms as if they were disease manifestations. However, viewing diseases such as panic disorder, melancholia and schizophrenia as if they are adaptations is an equally serious mistake in evolutionary psychiatry. Progress will come from framing and testing specific hypotheses about why natural selection left us vulnerable to mental disorders. The efforts of many people over many years will be needed before we will know if evolutionary biology can provide a new paradigm for understanding and treating mental disorders.

On the Embodiment of Social Cognition Skills: The Inner and Outer Body Processing Differently Contributes to the Affective and Cognitive Theory of Mind

A specific interpretation of embodiment assigns a central role to the body representations (BR) in cognition. In the social cognition domain, BR could be pivotal in representing others' actions and states. However, empirical evidence on the relationship between different BR and social cognition, in terms of Theory of Mind (ToM), in the same sample of participants is missing. Here, this relationship was explored considering individual differences in the action-oriented BR (aBR), nonaction-oriented BR (NaBR), and subjective predisposition toward internal bodily sensations (interoceptive sensibility, ISe). Eighty-two healthy adults were given behavioral measures probing aBR, NaBR, ISe, and affective/cognitive ToM. The results suggest that NaBR, which mainly relies on exteroceptive signals, predicts individual differences in cognitive ToM, possibly because it can allow differentiating between the self and others. Instead, the negative association between affective ToM and ISe suggests that an alteration of the internal body state representation (i.e., over-reporting interoceptive sensations) can affect emotional processing in social contexts. The finding that distinct aspects of the body processing from within (ISe) and from the outside (NaBR) differently contribute to ToM provides empirical support to the BR role in social cognition and can be relevant for developing interventions in clinical settings.

Generalized Simultaneous Localization and Mapping (G-SLAM) as unification framework for natural and artificial intelligences: towards reverse engineering the hippocampal/entorhinal system and principles of high-level cognition

Simultaneous localization and mapping (SLAM) represents a fundamental problem for autonomous embodied systems, for which the hippocampal/entorhinal system (H/E-S) has been optimized over the course of evolution. We have developed a biologically-inspired SLAM architecture based on latent variable generative modeling within the Free Energy Principle and Active Inference (FEP-AI) framework, which affords flexible navigation and planning in mobile robots. We have primarily focused on attempting to reverse engineer H/E-S "design" properties, but here we consider ways in which SLAM principles from robotics may help us better understand nervous systems and emergent minds. After reviewing LatentSLAM and notable features of this control architecture, we consider how the H/E-S may realize these functional properties not only for physical navigation, but also with respect to high-level cognition understood as generalized simultaneous localization and mapping (G-SLAM). We focus on loop-closure, graph-relaxation, and node duplication as particularly impactful architectural features, suggesting these computational phenomena may contribute to understanding cognitive insight (as proto-causal-inference), accommodation (as integration into existing schemas), and assimilation (as category formation). All these operations can similarly be describable in terms of structure/category learning on multiple levels of abstraction. However, here we adopt an ecological rationality perspective, framing H/E-S functions as orchestrating SLAM processes within both concrete and abstract hypothesis spaces. In this navigation/search process, adaptive cognitive equilibration between assimilation and accommodation involves balancing tradeoffs between exploration and exploitation; this dynamic equilibrium may be near optimally realized in FEP-AI, wherein control systems governed by expected free energy objective functions naturally balance model simplicity and accuracy. With respect to structure learning, such a balance would involve constructing models and categories that are neither too inclusive nor exclusive. We propose these (generalized) SLAM phenomena may represent some of the most impactful sources of variation in cognition both within and between individuals, suggesting that modulators of H/E-S functioning may potentially illuminate their adaptive significances as fundamental cybernetic control parameters. Finally, we discuss how understanding H/E-S contributions to G-SLAM may provide a unifying framework for high-level cognition and its potential realization in artificial intelligences.

Bottom-up vs. top-down connectivity imbalance in individuals with high-autistic traits: An electroencephalographic study

Brain connectivity is often altered in autism spectrum disorder (ASD). However, there is little consensus on the nature of these alterations, with studies pointing to either increased or decreased connectivity strength across the broad autism spectrum. An important confound in the interpretation of these contradictory results is the lack of information about the directionality of the tested connections. Here, we aimed at disambiguating these confounds by measuring differences in directed connectivity using EEG resting-state recordings in individuals with low and high autistic traits. Brain connectivity was estimated using temporal Granger Causality applied to cortical signals reconstructed from EEG. Between-group differences were summarized using centrality indices taken from graph theory (in degree, out degree, authority, and hubness). Results demonstrate that individuals with higher autistic traits exhibited a significant increase in authority and in degree in frontal regions involved in high-level mechanisms (emotional regulation, decision-making, and social cognition), suggesting that anterior areas mostly receive information from more posterior areas. Moreover, the same individuals exhibited a significant increase in the hubness and out degree over occipital regions (especially the left and right pericalcarine regions, where the primary visual cortex is located), suggesting that these areas mostly send information to more anterior regions. Hubness and authority appeared to be more sensitive indices than the in degree and out degree. The observed brain connectivity differences suggest that, in individual with higher autistic traits, bottom-up signaling overcomes top-down channeled flow. This imbalance may contribute to some behavioral alterations observed in ASD.

The Atypical Effective Connectivity of Right Temporoparietal Junction in Autism Spectrum Disorder: A Multi-Site Study

Social function impairment is the core deficit of autism spectrum disorder (ASD). Although many studies have investigated ASD through a variety of neuroimaging tools, its brain mechanism of social function remains unclear due to its complex and heterogeneous symptoms. The present study aimed to use resting-state functional magnetic imaging data to explore effective connectivity between the right temporoparietal junction (RTPJ), one of the key brain regions associated with social impairment of individuals with ASD, and the whole brain to further deepen our understanding of the neuropathological mechanism of ASD. This study involved 1,454 participants from 23 sites from the Autism Brain Imaging Data Exchange (ABIDE) public dataset, which included 618 individuals with ASD and 836 with typical development (TD). First, a voxel-wise Granger causality analysis (GCA) was conducted with the RTPJ selected as the region of interest (ROI) to investigate the differences in effective connectivity between the ASD and TD groups in every site. Next, to obtain further accurate and representative results, an image-based meta-analysis was implemented to further analyze the GCA results of each site. Our results demonstrated abnormal causal connectivity between the RTPJ and the widely distributed brain regions and that the connectivity has been associated with social impairment in individuals with ASD. The current study could help to further elucidate the pathological mechanisms of ASD and provides a new perspective for future research.

Autistic-Like Traits and Positive Schizotypy as Diametric Specializations of the Predictive Mind

According to the predictive-processing framework, only prediction errors (rather than all sensory inputs) are processed by an organism's perceptual system. Prediction errors can be weighted such that errors from more reliable sources will be more influential in updating prior beliefs. It has previously been argued that autism-spectrum conditions can be understood as resulting from a predictive-processing mechanism in which an inflexibly high weight is given to sensory-prediction errors that results in overfitting their predictive models to the world. Deficits in executive functioning, theory of mind, and central coherence are all argued to flow naturally from this core underlying mechanism. The diametric model of autism and psychosis suggests a simple extension of this hypothesis. If people on the autism spectrum give an inflexibly high weight to sensory input, could it be that people with a predisposition to psychosis (i.e., people high in positive schizotypy) give an inflexibly low weight to sensory input? In this article I argue that evidence strongly supports this hypothesis. An inflexibly low weight given to sensory input can explain such disparate features of positive schizotypy as increased exploratory behavior, apophenia, hyper theory of mind, hyperactive imagination, attentional differences, and having idiosyncratic worldviews.

How selves differ within and across cognitive domains: self-prioritisation, self-concept, and psychiatric traits

Background

How we build and maintain representations of ourselves involves both explicit features which are consciously accessible on reflection and implicit processes which are not, such as attentional biases. Understanding relations between different ways of measuring self-cognition both within and across such cognitive domains is important for understanding how selves may differ from one another, and whether self-cognition is best understood as largely uni-dimensional or more multi-dimensional. Further, uncovering this structure should inform research around how self-cognition relates to psychiatric and psychological conditions. This study explores the relations between different constructs of self-cognition and how variability within them relates to psychiatric traits.

Methods

Our final dataset includes within-subject (n = 288, general population) measures of explicit self-concept (using both the Self Concept Clarity Scale and Self Concept and Identity Measure), implicit self-prioritisation in a shape-label matching task (for both reaction time and sensitivity) and measurement of traits for five psychiatric conditions (autism, borderline personality disorder, schizophrenia, depression and anxiety). We first test whether self-cognitive measures within and across domains are correlated within individuals. We then test whether these dimensions of self-cognition support a binary distinction between psychiatric conditions that either are or are not characterised in terms of self, or whether they support self-cognition as transdiagnostically predictive of the traits associated with psychiatric conditions. To do this we run a series of planned correlations, regressions, and direct correlation comparison statistics.

Results

Results show that implicit self-prioritisation measures were not correlated with the explicit self-concept measures nor the psychiatric trait measures. In contrast, all the psychiatric traits scores were predicted, to varying degrees, by poorer explicit self-concept quality. Specifically, borderline personality disorder traits were significantly more strongly associated with composite explicit self-concept measures than any of depression, anxiety, or autism traits scores were.

Conclusions

Our results suggest that selves can differ considerably, along different cognitive dimensions. Further, our results show that self-cognition may be a promising feature to include in future dimensional characterisations of psychiatric conditions, but care should be taken to choose relevant self-cognitive domains.

Is Alexithymia the Link Between Anorexia and Autism Spectrum Disorders?

Objective

Alexithymia main features include deficits in empathy, emotion recognition and regulation. Alexithymia has been recently proposed as a potential key to explain the presence of the so-called 'autistic spectrum disorder' signs (ASD), in patients with Anorexia Nervosa (AN). Objective of this review is to summarize current knowledge on the potential role of alexithymia in linking ASD and AN.

Method

A systematic search has been conducted on PUBMED database of the last 10 years, in accordance with PRISMA Guidelines, applying queries in the 'PubMed Advanced Search Builder'.

Results

We initially retrieved 18 papers; the final selection has led to seven papers. According to the available studies, alexithymia is widely represented in samples of AN patients and comorbid ASD traits. However, the specific load of alexithymia in AN with ASD features is still in debate, as well as the potential role of interoceptive deficits. We have found several limitations in the reviewed studies, which shared a cross-sectional design, with no comparison between a pre and a post-treatment condition (except for one study), small samples sizes and some heterogeneity of administered instruments.

Conclusions

the specific load of alexithymia in explaining the link between AN and ASD is still in debate. Interoception deficit has been proposed as having a crucial role. Further research should be devoted to longitudinal studies and not only to cross-sectional observations.

Deficits in Sense of Body Ownership, Sensory Processing, and Temporal Perception in Schizophrenia Patients With/Without Auditory Verbal Hallucinations

It has been claimed that individuals with schizophrenia have difficulty in self-recognition and, consequently, are unable to identify the sources of their sensory perceptions or thoughts, resulting in delusions, hallucinations, and unusual experiences of body ownership. The deficits also contribute to the enhanced rubber hand illusion (RHI; a body perception illusion, induced by synchronous visual and tactile stimulation). Evidence based on RHI paradigms is emerging that auditory information can make an impact on the sense of body ownership, which relies on the process of multisensory inputs and integration. Hence, we assumed that auditory verbal hallucinations (AVHs), as an abnormal auditory perception, could be linked with body ownership, and the RHI paradigm could be conducted in patients with AVHs to explore the underlying mechanisms. In this study, we investigated the performance of patients with/without AVHs in the RHI. We administered the RHI paradigm to 80 patients with schizophrenia (47 with AVHs and 33 without AVHs) and 36 healthy controls. We conducted the experiment under two conditions (synchronous and asynchronous) and evaluated the RHI effects by both objective and subjective measures. Both patient groups experienced the RHI more quickly and strongly than HCs. The RHI effects of patients with AVHs were significantly smaller than those of patients without AVHs. Another important finding was that patients with AVHs did not show a reduction in RHI under asynchronous conditions. These results emphasize the disturbances of the sense of body ownership in schizophrenia patients with/without AVHs and the associations with AVHs. Furthermore, it is suggested that patients with AVHs may have multisensory processing dysfunctions and internal timing deficits.

Past and Future Explanations for Depersonalization and Derealization Disorder: A Role for Predictive Coding

Depersonalization (DP) and derealization (DR) refer to states of dissociation in which one feels a sense of alienation in relation to one's self and environment, respectively. Whilst transient episodes often diminish without treatment, chronic experiences of DP and DR may last for years, with common treatments lacking a strong evidence base for their efficacy. We propose a theoretical explanation of DP and DR based on interoceptive predictive coding, and discuss how transient experiences of DP and DR may be induced in the non-clinical population using virtual reality. Further, we review the use of heartbeat evoked potentials in detecting the neural correlates of DP and DR allowing for an objective measure of these experiences in the non-clinical population. Finally, we discuss how the induction and detection of transient experiences of DP and DR in the non-clinical population could shed light on how the brain constructs one's sense of self and reality.

Bodies in the Novel Infinite Jest

This manuscript provides a literary analysis of the use of bodies in the novel Infinite Jest by David Foster Wallace. The novel describes a world where oversaturation of external stimulation leads to the perception of mind and body of self of an individual as prosthetic parts, malleable and deformed, wherein the mind fails to feel bodily sensations and characters experience a complete disconnectedness from the self and others. Indeed, the disembodiment of characters and sensations of disconnection leads them to a compulsive quest for connectedness through the use of masks, made-up feelings, mind-body hybrid pain, corporeal malleability, and prostheses. These portrayals of the disordered and disconnectedness between body and mind or self will be described and compared to clinical conditions characterized by a disconnection between mind and body and impaired body self-awareness. Through this exercise, we argue that the use of scientifically inspired pathologized bodies is a means of conveying the stance of Wallace on or criticism of the degradation of society through excessive entertainment.

Visual-Tactile Spatial Multisensory Interaction in Adults With Autism and Schizophrenia

Background: Individuals with autism spectrum disorder (ASD) and schizophrenia (SZ) exhibit multisensory processing difficulties and social impairments, with growing evidence that the former contributes to the latter. However, this work has largely reported on separate cohorts, introducing method variance as a barrier to drawing broad conclusions across studies. Further, very few studies have addressed touch, resulting in sparse knowledge about how these two clinical groups may integrate somatic information with other senses. Methods: In this study, we compared adults with ASD (n = 29), SZ (n = 24), and typical developmental histories (TD, n = 37) on two tasks requiring visual-tactile spatial multisensory processing. In the first task (crossmodal congruency), participants judged the location of a tactile stimulus in the presence or absence of simultaneous visual input that was either spatially congruent or incongruent, with poorer performance for incongruence an index of spatial multisensory interaction. In the second task, participants reacted to touch in the presence or absence of dynamic visual stimuli that appeared to approach or recede from the body. Within a certain radius around the body, defined as peripersonal space (PPS), an approaching visual or auditory stimulus reliably speeds reaction times (RT) to touch; outside of this radius, in extrapersonal space (EPS), there is no multisensory effect. PPS can be defined both by its size (radius) and slope (sharpness of the PPS-EPS boundary). Clinical measures were administered to explore relations with visual-tactile processing. Results: Neither clinical group differed from controls on the crossmodal congruency task. The ASD group had significantly smaller and more sharply-defined PPSs compared to the other two groups. Small PPS size was related to social symptom severity across groups, but was largely driven by the TD group, without significant effects in either clinical group. Conclusions: These results suggest that: (1) spatially static visual-tactile facilitation is intact in adults with ASD and SZ, (2) spatially dynamic visual-tactile facilitation impacting perception of the body boundary is affected in ASD but not SZ, and (3) body boundary perception is related to social-emotional function, but not in a way that maps on to clinical status.

The Right Temporoparietal Junction Is Causally Associated with Embodied Perspective-taking

A prominent theory claims that the right temporoparietal junction (rTPJ) is especially associated with embodied processes relevant to perspective-taking. In the present study, we use high-definition transcranial direct current stimulation to provide evidence that the rTPJ is causally associated with the embodied processes underpinning perspective-taking. Eighty-eight young human adults were stratified to receive either rTPJ or dorsomedial PFC anodal high-definition transcranial direct current stimulation in a sham-controlled, double-blind, repeated-measures design. Perspective-tracking (line-of-sight) and perspective-taking (embodied rotation) were assessed using a visuo-spatial perspective-taking task that required understanding what another person could see or how they see it, respectively. Embodied processing was manipulated by positioning the participant in a manner congruent or incongruent with the orientation of an avatar on the screen. As perspective-taking, but not perspective-tracking, is influenced by bodily position, this allows the investigation of the specific causal role for the rTPJ in embodied processing. Crucially, anodal stimulation to the rTPJ increased the effect of bodily position during perspective-taking, whereas no such effects were identified during perspective-tracking, thereby providing evidence for a causal role for the rTPJ in the embodied component of perspective-taking. Stimulation to the dorsomedial PFC had no effect on perspective-tracking or taking. Therefore, the present study provides support for theories postulating that the rTPJ is causally involved in embodied cognitive processing relevant to social functioning.SIGNIFICANCE STATEMENT The ability to understand another's perspective is a fundamental component of social functioning. Adopting another perspective is thought to involve both embodied and nonembodied processes. The present study used high-definition transcranial direct current stimulation (HD-tDCS) and provided causal evidence that the right temporoparietal junction is involved specifically in the embodied component of perspective-taking. Specifically, HD-tDCS to the right temporoparietal junction, but not another hub of the social brain (dorsomedial PFC), increased the effect of body position during perspective-taking, but not tracking. This is the first causal evidence that HD-tDCS can modulate social embodied processing in a site-specific and task-specific manner.